Bin son: V NH HONG http://lophocthem.net - vuhoangbg@gmail.com T:01689.996.187BI DNG, N LUYN THI VO I HC. Thi Nguyn,24/4/ 2012 LI NI U! Tha thy c cng ton th cc bn hc sinh!SAU THI GIAN DI BIN TP CHNH SA LI, HM NAY XIN GI TI THY C V CC EM HC SINH TRN B TI LIU CA MNH. LN TI BN NY CP NHT PHN DNG TNG DNG BI TON VI V D MINH HA C TH CHO TNG DNG, CP NHT THM CC CH MI.Ti liu c dy cng bin son v c th nghim kim tra, tuyn chn, chnh sa qua nhiu th h hc sinh. VI TT C TM HUYT V SC LC CA MNH. Mong rng qu thy c, cc bn hc sinh n nhn trn trng n. Hy vng y thc s l 1 b ti liu y , chi tit, cng phu cho qu thy c cng cc bn hc sinh tham kho. B ti liu s gip ch rt nhiu cho vic n tp, rn luyn cho cc em hc sinh 12 trc k thi i Hc ang ti gn . Cu trc gm: 9 chng vi41 chuyn Chuong 1. co hoc vat ran ( s 0) PHN DNG BI TP C HC VT RN KIM TRA C HC VT RN S 1 KIM TRA C HC VT RN S 2 Chuong 2. Dao dong co ( s 1- 12) Chu de 1. Dai cuong ve dao dong dieu hoa Chu de 2. Con lac lo xo Chu de 3. Con lac don Chu de 4. Cac loai dao dong. Cong huong co Chu de 5. Do lech pha. Tong hop dao dong Chu de 6. CHUONG DAO DONG de thi h cac nam Chuong 3. Song co ( s 13- 16) Chu de 1. Dai cuong ve song co Chu de 2. Giao thoa song co Chu de 3. Su phan xa song. Song dung Chu de 4. Song am. Hieu ung Doppler. chu de 5. SNG C HC THI AI HC + CAO NG CC NM Chuong 4. Dong dien xoay chieu ( s 17- 24) Chu de 1. Dai cuong ve dong dien xoay chieu. Chu de 2. Hien tuong cong huong. Viet bieu thuc Chu de 3. Cong suat cua dong dien xoay chieu Chu de 4. Mach co R, L , C hoac f bien doi. Chu de 5. Do lech pha. BT hop den. Chu de 6. Phuong phap gian do vecto. Chu de 7. Cac loai may dien. Chu de 8. DNG IN XOAY CHIU THI AI HC + CAO NG CC NM Chuong 5. Mach dao dong. Dao dong va song dien tu ( s 25-27) Chu de 1. MCH DAO NG. DAO NG IN T -s 1 Chu de 2. MCH DAO NG. DAO NG IN T -s 2 Chu de 3. IN T TRNG. SNG IN T. TRUYN THNG Chu de 4. SNG IN T THI AI HC + CAO NG CC NM Chuong 6. Song anh sang ( s 28-31). CH 1.TN SC NH SNG. CH 2.GIAO THOA NH SNG S 1, S 2 CH 3. QUANG PH V CC LOI TIA. CH 4.SNG NH SNG THI AI HC + CAO NG CC NM Chuong 7. Luong tu anh sang ( s 32- 35) CH 1.HIN TNG QUANG IN S 1, S 2 CH 2. MU NGUYN T BO. QUANG PH NGUYN T HYDRO. CH 3. HP TH V PHN X LC LA MU SC NH SNG LAZE. CH 4. LNG T NH SNG THI AI HC + CAO NG CC NM Chuong 8. Hat nhan nguyen tu ( s 36-39) CH 1. I CNG V HT NHN NGUYN T. CH 2. PHNG X T NHIN. CH 3. PHN NG HT NHN. CH 4. PHN NG PHN HCH & PHN NG NHIT HCH. CH 5. HT NHN THI AI HC + CAO NG CC NM Chuong 9. Tu vi mo den vi mo ( s 40) De so 40 KIM TRA Tu vi mo den vi mo VI V M + PHN RING THI AI HC, CAO NG CC NM cmunthnhiumscngithchn,trongqutrnhbinsontiliu,visuy ngh ch quan theo cch hiu bn thn nn chc chn khng trnh khi iu sai st. c bit trong qu trnh chn lc v phn dng bi tp. MikinnggpvchiasbnquynfileWord,tiliuthmhonthinhy lin h trc tip cho thy V nh Hong.Mail:vuhoangbg@gmail.com forum: lophocthem.net T: 01689.996.187 Vuhoangbg Chcquthycvccbnmnhkhe,hnhphcbnhan,chcccemhcsinhmt ma thi thnh cng, t! Xin chn thnh cm n! TI LIU THAM KHO 1.CHUYN BI TP LTH - THY MINH TU - BC GIANG 2. SNG KIN KINH NGHIM- Phng php gii cc dng bi tp Vt l 12-Dng Vn ng Trng THPT Nguyn Vn Linh, Bnh Thun 3. Vt l 12 - Nng cao - V Thanh Khit (ch bin) - NXB GD - Nm 2011. 4. Bi tp vt l 12 - Nng cao - V Thanh Khit (ch bin) - NXB GD - Nm 2011. 9. Cc thi tt nghip THPT v tuyn sinh H - C cc nm 2009, 2010 v 2011. 10.Cctiliutruycptrncctrangwebthuvienvatly.comvviolet.vn.onthi.vn hocmai.vn tailieu.vn.....v cc trang mng hc tp khc 11. n tp LT+BT Sng nh sng- Gio vin: Trn Thanh Vn - Trng THPT Ph in 12. SCH 200 BI TON IN XOAY CHIU 13. SCH 206 BI TON IN XOAY CHIU, DAO NG V SNG IN T -TS PHM TH DN. 14. SCH MT S PHNG PHP CHN LC GII CC BI TON VT L S CP GS: V THANH KHIT15. cng n tp Vt l 12- Hc k II- Nm hc 2010-2011- T Vt l - Trng THPT Trn Quc Tun 16. SNG C - Trn Quang Thanh - H Vinh -Ngh An - 2011 17. Sng kin kinh nghim NGUY THANH VN 18. CC DNG BI TP VT L 12 THY Ngha 19. PHN DNG V HNG D GII TON C HC IN XOAY CHIU. 20. GII TON NG TRN LNG GIC - GV Trn Huy DngTrng THPT Thng Nht 21. TNH CHT SNG NH SNG- ThS. Lin Quang Thnh 22. SCH PHNG PHP GII QUANG L-VT L HT NHN TRN TRNG HNG V nhiu ngun ti liu khc khng r tc gi .Nu c s vi phm bn quyn tc gi xin lng th v thng bo li vi Hong theo a ch mail trn.

-T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN1 H v tn hc sinh :................................................Trng:THPT............................................ I. KIN THC CHUNG. 1. To gc Khi vt rn quay quanh mt trc c nh (hnh 1) th : - Mi im trn vt vch mt ng trn nm trong mt phng vung gc vi trc quay, c bn knh r bng khong cch t im n trc quay, c tm O trn trc quay. - Mi im ca vt u quay c cng mt gc trong cng mt khong thi gian. Trnhnh1,vtrcavttimithiimcxcnhbnggcgiamtmt phngngP gn vi vt vmtmtphng cnhP0(hai mtphngnyucha trc quay Az). Gc c gi l to gc ca vt. Gc c o bng raian, k hiu l rad. Khi vt rn quay, s bin thin ca theo thi gian t th hin quy lut chuyn ng quay ca vt. 2.Tc gc Tc gc l i lng c trng cho mc nhanh chm ca chuyn ng quay ca vt rn. thi im t, to gc ca vt l . thi im t + t, to gc ca vt l + . Nh vy, trong khong thi gian t, gc quay ca vt l . Tc gc trung bnh tb ca vt rn trong khong thi gian t l :

ttb= (1.1) Tc gc tc thi thi im t (gi tt l tc gc) c xc nh bng gii hn ca t s t khi cho t dn ti 0. Nh vy :

tt= 0limhay) ('t = (1.2) n v ca tc gc l rad/s. 3.Gia tc gc Ti thi im t, vt c tc gc l . Ti thi im t + t, vt c tc gc l + . Nh vy, trong khong thi gian t, tc gc ca vt bin thin mt lng l . Gia tc gc trung bnh tb ca vt rn trong khong thi gian t l :

ttb= (1.3) Gia tc gc tc thi thi im t (gi tt l gia tc gc) c xc nh bng gii hn ca t s t khi cho t dn ti 0. Nh vy :

tt= 0limhay) ('t = (1.4) n v ca gia tc gc l rad/s2. 4. Cc phng trnh ng hc ca chuyn ng quay a)Trng hp tc gc ca vt rn khng i theo thi gian ( = hng s, = 0) th chuyn ng quay ca vt rn l chuyn ng quay u. Chn gc thi gian t = 0 lc mt phng P lch vi mt phng P0 mt gc 0, t (1) ta c : CHUYN : C HC VT RN -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN2 = 0 + t (1.5) b)Trng hp gia tc gc ca vt rn khng i theo thi gian ( = hng s) th chuyn ng quay ca vt rn l chuyn ng quay bin i u. Cc phng trnh ca chuyn ng quay bin i u ca vt rn quanh mt trc c nh : t + =0(1.6)

20 021t t + + = (1.7) ) ( 20202 = (1.8) trong 0 l to gc ti thi im ban u t = 0. 0 l tc gc ti thi im ban u t = 0. l to gc ti thi im t. l tc gc ti thi im t. l gia tc gc ( = hng s). Nu vt rn ch quay theo mt chiu nht nh v tc gc tng dn theo thi gian th chuyn ng quay l nhanh dn. Nu vt rn ch quay theo mt chiu nht nh v tc gc gim dn theo thi gian th chuyn ng quay l chm dn. 5.Vn tc v gia tc ca cc im trn vt quay Tc di v ca mt im trn vt rn lin h vi tc gc ca vt rn v bn knh qu o r ca im theo cng thc : r v = (1.9) Nu vt rn quay u th mi im ca vt chuyn ng trn u. Khi vect vn tcvr ca mi im ch thay i v hng m khng thay i v ln, do mi im ca vt c gia tc hng tm nar vi ln xc nh bi cng thc : rrvan22 = = (1.10) Nu vt rn quay khng u th mi im ca vt chuyn ng trn khng u. Khi vect vn tcvr ca mi im thay i c v hng v ln, do mi im ca vt c gia tcar (hnh 2) gm hai thnh phn : + Thnh phn nar vung gc vivr, c trng cho s thay i v hng cavr, thnh phn ny chnh l gia tc hng tm, c ln xc nh bi cng thc : rrvan22 = = (1.11) + Thnh phn tar c phng cavr, c trng cho s thay i v ln cavr, thnh phn ny c gi l gia tc tip tuyn, c ln xc nh bi cng thc : rtvat== (1.12) Vect gia tcar ca im chuyn ng trn khng u trn vt l :

t na a ar r r+ = (1.13) V ln : 2 2t na a a + =(1.14) Vect gia tcar ca mt im trn vt rn hp vi bn knh OM ca n mt gc , vi : vr tar nar ar r O M Hnh 2 -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN3 2tan = =ntaa(1.15) (1.15) II. TRC NGHIM L THUYT TNG HP. 1. Trong chuyn ng quay ca vt rn quanh mt trc c nh, mi im ca vt c A. qu o chuyn ng ging nhau.B. cng ta gc. C. tc gc quay bng nhau. D. tc di bng nhau. 2. Mt vt rn quay u xung quanh mt trc. Mt im ca vt cch trc quay mt khong l R th c: A. tc gc cng ln nu R cng ln. B. tc gc cng ln nu R cng nh. C. tc di cng ln nu R cng ln. D. tc di cng ln nu R cng nh. 3.MtimtrntrcrncchtrcquaymtkhongR.Khivtrnquayuquanhtrc, im c tc di l v. Tc gc ca vt rn l: A. = RvB. = Rv2C. = vRD. = vR

4.Khimtvtrnquayuxungquanh mttrccnh i quavtthmtimcavt cch trc quay mt khong l R 0 c: A. vc t vn tc di khng i.B. ln vn tc gc bin i. C. ln vn tc di bin i. D. vc t vn tc di bin i. 5. Khi mt vt rn ang quay xung quanh mt trc c nh i qua vt, mt im ca vt cch trc quay mt khong l R 0 c ln ca gia tc tip tuyn lun bng khng. Tnh cht chuyn ng ca vt rn l: A. quay chm dn.B. quay u. C. quay bin i u.D. quay nhanh dn u. 6. Mt a phng ang quay quanh trc c nh i qua tm v vung gc vi mt phng a vi tc gc khng i. Mt im bt k nm mp a A. khng c c gia tc hng tm v gia tc tip tuyn. B. ch c gia tc hng tm m khng c gia tc tip tuyn. C. ch c gia tc tip tuyn m khng c gia tc hng tm.D. c c gia tc hng tm v gia tc tip tuyn.7. Khi mt vt rn quay xung quanh mt trc c nh xuyn qua vt, cc im trn vt rn (khng thuc trc quay): E. c gia tc gc tc thi khc nhau. F. quay c nhng gc quay khng bng nhau trong cng mt khong thi gian. G. c tc gc tc thi bng nhau. H. c cng tc di tc thi. 8. Chn cu sai. A.Vn tc gc v gia tc gc l cc i lng c trng cho chuyn ng quay ca vt rn. B. ln ca vn tc gc gi l tc gc. C.Nu vt rn quay u th gia tc gc khng i. D.Nu vt rn quay khng u th vn tc gc thay i theo thi gian. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN4 9. Khi mt vt rn ang quay xung quanh mt trc c nh i qua vt, mt im ca vt cch trc quay mt khong l R 0 c ln vn tc di ph thuc vo thi gian t theo biu thc v = 5t (m/s). Tnh cht chuyn ng ca vt rn l: A. quay chm dn.B. quay u. C. quay bin i u.D. quay nhanh dn u.10. Chn cu tr li ng: Mt vt chuyn ng trn trn ng trn bn knh R vi tc gc, vc t vn tc di: I.c phng vung gc vi bn knh qu o R. J. c phng tip tuyn vi qu o. K. c ln v = R. L. C A, B, C u ng. 11. Vect gia tc tip tuyn ca mt cht im chuyn ng trn chm dn u: A.c phng vung gc vi vect vn tc. B.cng phng, cng chiu vi vect vn tc. C.cng phng vi vect vn tc. D.cng phng, ngc chiu vi vect vn tc. 12. Vect gia tc php tuyn ca mt cht im chuyn ng trn u: A.bng 0. B.c phng vung gc vi vect vn tc. C.cng phng vi vect vn tc. D.cng phng, cng chiu vi vect vn tc.13. Khi mt vt rn ang quay chm dn u xung quanh mt trc c nh xuyn qua vt th: A. gia tc gc lun c gi tr m. B. tch tc gc v gia tc gc l s dng. C. tch tc gc v gia tc gc l s m.D. tc gc lun c gi tr m.14.Giatchngtmcamtvtrn(ccoinhmtchtim)chuynngtrn khng u: A.nh hn gia tc tip tuyn ca n. B.bng gia tc tip tuyn ca n. C.ln hn gia tc tip tuyn ca n. D.c th ln hn, nh hn hay bng gia tc tip tuyn ca n. 15. Gia tc ton phn ca mt vt rn (c coi nh mt cht im) chuyn ng trn khng u: A. nh hn gia tc tip tuyn ca n.B. bng gia tc tip tuyn ca n. C. ln hn gia tc tip tuyn ca n. D.cthlnhn,nhhnhaybnggiatc tip tuyn ca n. 16. Phng trnh no sau y biu din mi quan h gia tc gc v thi gian t trong chuyn ng quay nhanh dn u ca vt rn quay quanh mt trc c nh? A. = -5 + 4t(rad/s)B. = 5 - 4t(rad/s) C. =5 + 4t2(rad/s)D. = - 5 - 4t(rad/s) 17. Mt vt rn chuyn ng u vch nn qu o trn, khi gia tc: A. a = atB. a = anC. a = 0D. C A, B, C u sai. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN5 trong : a = gia tc ton phn; at = gia tc tip tuyn; an = gia tc php tuyn (gia tc hng tm). 18.Trongchuynngquaybiniumtimtrnvtrn,vectgiatctonphn (tng vect gia tc tip tuyn v vect gia tc hng tm) ca im y A. c ln khng i. B. C hng khng i. C. c hng v ln khng i. D. Lun lun thay i. 19. Mt vt rn quay nhanh dn u xung quanh mt trc c nh. Sau thi gian t k t lc vt bt u quay th gc m vt quay c A. t l thun vi t. B. t l thun vi t2. C. t l thun vit . D. t l nghch vi t . 20. Trong chuyn ng quay ca vt rn quanh mt trc c nh, mi im ca vtA. u quay c cng mt gc trong cng mt khong thi gian.B. quay c cc gc khc nhau trong cng khong thi gian. C. c cng ta gc.D. c qu o trn vi bn knh bng nhau. 21. Mt vt rn ang quay quanh mt trc c nh i qua vt , mt im xc nh trn vt rn cch trc quay khang r0 c ln vn tc di l mt hng s . Tnh cht chuyn ng ca vt rn l A. quay chm dnB. quay uC. quay bin i uD. quay nhanh dn 22. Mt vt rn quay bin i u quanh mt trc c nh i qua vt. Mt im xc nh trn vt rn cch trc quay khong r0 c A. tc gc khng bin i theo thi gian. B. gia tc gc bin i theo thi gianC. ln gia tc tip tuyn bin i theo thi gian D. tc gc bin i theo thi gian23. Mt vt rn quay bin i u quanh mt trc c nh i qua vt. Mt im xc nh trn vt rn v khng nm trn trc quay c: A.lncagiatctiptuynthayi.B.giatcgclunbinthintheothi gian.C. gia tc hng tm lun hng vo tm qu o trn ca im .D. tc di bin thin theo hm s bc hai ca thi gian. 24. Chn cu Sai. Trong chuyn ng ca vt rn quanh mt trc c nh th mi im ca vt rn: A. c cng gc quay. B. c cng chiu quay. C. u chuyn ng trn cc qu o trn.D.uchuynngtrongcng mt mt phng. 25. Mt vt rn quay u xung quanh mt trc, mt im M trn vt rn cch trc quay mt khong Rth c A. tc gc t l thun vi R; B. tc gc t l nghch vi R C. tc di v t l thun vi R;D. tc di v t l nghch vi R 26. Pht biu no sau y l khng ng i vi chuyn ng quay u ca vt rn quanh mt trc ?-T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN6 A. Tc gc l mt hm bc nht ca thi gian. B.Giatcgccavtbng 0.C. Trong nhng khong thi gian bng nhau, vt quay c nhng gc bng nhau. D. Phng trnh chuyn ng (pt to gc) l mt hm bc nht ca thi gian. 27. Mt vt rn quay quanh trc c nh i qua vt. Mt im c nh trn vt rn nm ngoi trc quay c tc gc khng i. Chuyn ng quay ca vt rn l quay A.u.B.nhanh dn u. C.bin i u. D.chm dn u. 28 Khi vt rn quay u quanh trc c nh vi tc gc th mt im trn vt rn cch trc quay mt khong r c gia tc hng tm c ln bng: A. 2r.B. 2/r. C.0.D. r2. P N TRC NGHIM PHN L THUYT 1C2C3A4D5B6B7G8C9D10L 11 D12B13C14D15C16D17B18D19B20A 21 B22D23C24D25C26A27A28A CH 1. CHUYN NG QUAY QUANH TRC CA VT RN I.CC DNG BI TP DNG 1: VT RN QUAY U QUANH MT TRC C NH Tc gc:const =Gia tc gc:0 = Ta gc: 0t = +Gc quay:.t =Cng thc lin h: r v =22 fT = =22.nva rr = =* TRC NGHIM TNG HP: 1. Mt a c ng cht c dng hnh trn bnh knh R ang quay trn u quanh trc ca n.TsgiatchngtmcaimNtrnvnhaviimMcchtrcquaymt khong cch bng na bn knh ca a bng: A. 12B. 1C. 2D. 4 2. Mt xe p c bnh xe ng knh 700 mm, chuyn ng u vi tc 12,6 km/h. Tc gc ca u van xe p l: A. 5 rad/sB. 10 rad/sC. 20 rad/sD. Mt gi tr khc. 3. Mt vt hnh cu bn knh R = 25 m, chuyn ng quay u quanh mt trc thng ng i qua tm ca n. Khi mt im A trn vt, nm xa trc quay nht chuyn ng vi tc 36 km/h. Gia tc hng tm ca A bng: A. 0,4 m/s2 B. 4 m/s2 C. 2,5 m/s2D. Mt gi tr khc.4. Mt a c ng cht c dng hnh trn bnh knh R = 30 cm ang quay trn u quanh trc ca n, thi gian quay ht 1 vng l 2 s. Bit rng im A nm trung im gia tm O ca vng trn vi vnh a. Tc di ca im Al: A. 47 cm/sB. 4,7 cm/sC. 94 cm/s D. 9,4 cm/s 5. Mt a c ng cht c dng hnh trn bnh knh R ang quay trn u quanh trc ca n. Hai im A, B nm trn cng mt ng knh ca a. im A nm trn vnh a, im -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN7 B nm trung im gia tm O ca vng trn vi vnh a. T s tc gc ca hai im A v B l: A.AB14=B. AB12=C. AB2= D. AB1= 6. Kim gi ca mt chic ng h c chiu di bng 3/4 chiu di kim pht. Coi nh cc kim quay u. T s tc gc ca u kim pht v u kim gi l A. 12; B. 1/12; C. 24; D. 1/24 7. Kim gi ca mt chic ng h c chiu di bng 3/4 chiu di kim pht. Coi nh cc kim quay u. T s gia vn tc di ca u kim pht v u kim gi l A. 1/16; B. 16; C. 1/9; D. 9 8. Kim gi ca mt chic ng h c chiu di bng 3/4 chiu di kim pht. Coi nh cc kim quay u. T s gia tc hng tm ca u kim pht v u kim gi l A. 92; B. 108; C. 192; D. 204 9. Mt bnh xe quay u xung quanh mt trc c nh vi tn s 3600 vng/min. Tc gc ca bnh xe ny l: A. 120 rad/s;B. 160 rad/s; C. 180 rad/s; D. 240 rad/s 10.Mtbnhxequayuxungquanhmttrccnhvitns3600vng/min.Trong thi gian 1,5s bnh xe quay c mt gc bng: A.90 rad; B.120 rad; C.150 rad;D.180 rad 11. Kim gi ca mt ng h c chiu di 8 cm. Tc di ca u kim l A.1,16.10-5 m/s.B.1,16.10-4 m/s. C.1,16.10-3 m/s.D.5,81.10-4 m/s. DNG 2: VT RN QUAY BIN I U QUANH MT TRC C NH Giatcgc: = const Tcgc: 0 = + t Tagc: 20 012 = + + t tTcgctb: tbt= Phng trnh c lp vi thi gian: 2 20 02 ( ) = Gc quay: 2012t t = + S vng quay: 2n=2n=Gia tc php tuyn:rdtdrdtdvatt. . = = = Gia tc hng tm:22.nva rr = =Gia tc:2 2 4 2.t na a a r = + = +*V d minh ha VD1. Phng trnh chuyn ng quay bin i u ca mt vt rn quanh mt trc c dng = 4 + 2t + 2t2 (rad). Tnh tc gc ca vt ti thi im t = 2 s. HD: So vi phng trnh: = 0 + 0t + 12 t2 th 0 = 4 rad; 0 = 2 rad/s; = 4 rad/s2. Thay t = 2 s vo phng trnh = 0 + t, ta c: = 10 rad/s. VD2. Mt chic qut in ang quay vi tc gc 1200 vng/pht th b mt in, sau 8 giy k t lc mt in, qut dng li hn. Coi chuyn ng quay ca qut sau khi mt in l chm dn u. Tnh gia tc gc v s vng qut quay c sau khi mt in. HD. Ta c: = 00 20.28 t = = - 5 (rad/s2); = 2 202 = 160 rad = 80 vng. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN8 VD3. Mt vt rn bt u quay nhanh dn u quanh mt trc c nh. Sau 5 giy k t lc bt u quay, n quay c mt gc 25 rad. Tnh vn tc gc m vt rn t c sau 15 s k t lc bt u quay. HD. Ta c: = 12 t2 (v 0 = 0) = 22t = 2 rad/s2; = 0 + t = 30 rad/s. VD4. Vt rn quay nhanh dn u t trng thi ngh. Trong giy th 2 vt quay c 3 vng. Hi trong 5 giy u tin vt quay c mt gc l bao nhiu? HD.V 0 = 0; 0 = 0 nn: = 12 .22 - 12 .12 = 3.2 rad = 4 rad/s25 = 12 .52 = 50 rad = 25 vng. VD5. T trng thi ngh, mt a bt u quay quanh mt trc c nh vi gia tc khng i. Sau 10 s, a quay c mt gc 50 rad. Tmgc m a quay c trong 10 s tip theo. HD.V 0 = 0 v 0 = 0 nn: 10 = 12 .102 = 50 rad = 2 rad/s2. Gc quay c trong 10 giy tip theo (t cui giy th 10 n cui giy th 20) l: = 12 .202 - 12 .102 = 150 rad. VD6. Mt vt rn quay nhanh dn u quanh mt trc c nh, trong 3,14 s tc gc ca n tng t 120 vng/pht n 300 vng/pht. Ly3,14 = . Tnh ln gia tc gc ca vt rn. HD.Ta c: = 0t = 3.2 2.23,14 = 2 rad/s2. VD7.Mtbnhxeangquayquanhmttrccnhvitcgc10rad/sthbhm. Bnh xe quay chm dn u, sau 5 s k t lc hm th dng hn. Tnh ln gia tc gc ca bnh xe. HD. Ta c: || = |0t | = |0 105| = 2 rad/s2. VD8. Mt vt rn quay chm dn u quanh mt trc quay c nh. Lc t = t1 vt c vn tc gc 1 = 10 rad/s. Sau khi quay c 10 vng th vt c vn tc gc 2 = 2 rad/s. Tnh gia tc gc ca chuyn ng quay. HD. Ta c: = 2 22 12 = 2 2 2 22 102.10.2 = - 2,4 rad/s2. VD9. Vt rn quay chm dn u vi vn tc gc ban u 0; quay c 20 vng th dng hn.Bittronggiycuicngtrckhidng,vtquaycmtvng.Tnhvntcgc ban u 0. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN9 HD. Gi t l thi gian quay t-1 l vn tc u trong giy cui th ta c: t = 0 = t-1 + .1t-1=-.Gcquayctronggiycuicng:=2= 2 2 210 ( )2 2t t = =-4 rad/s2. 0 =2 2.( 4 ).20.2 = = 8 5(rad/s). VD10. Mt cht im bt u chuyn ng nhanh dn trn mt ng trn bn knh 20 cm vigiatctiptuyn5cm/s2.Hisaubaoluktlcbt uchuynng,giatc tip tuyn bng gia tc php tuyn. HD. Ta c: at = r = tar = 0,25 rad/s2. Khi at = r = an = 2r th == 0,5 rad/st = 0 = 2 s. * TRC NGHIM TNG HP 12. Mt vt rn chuyn ng quay quanh mt trc vi ta gc l mt hm theo thi gian c dng: = 10t2 + 4 (rad; s). Ta gc ca vt thi im t = 2s l: A. 44 radB. 24 radC. 9 rad D. Mt gi tr khc. 13. Mt vt rn chuyn ng quay quanh mt trc vi ta gc l mt hm theo thi gian c dng: = 4t2(rad; s). Tc gc ca vt thi im t = 1,25 s l: A. 0,4 rad/sB. 2,5 rad/sC. 10 rad/sD. mt gi tr khc. 14. Mt xe p bt u chuyn ng trn mt ng hnh trn bn knh 400 m. Xe chuyn ng nhanh dn u, c saumt giy tc ca xe li tng thm 1m/s. Ti v tr trn qu omlncahaigiatchngtmvtiptuynbngnhau,thtcgccaxe bng: A. 0,05 rad/sB. 0,1 rad/sC. 0,2 rad/s D. 0,4 rad/s 15. Mt v lng quay vi tc gc 180 vng/pht th b hm chuyn ng chm dn u v dng li sau 12 s. S vng quay ca v lng t lc hm n lc dng li l: A. 6 vng B. 9 vngC. 18 vngD. 36 vng 16. Mt vt rn coi nh mt cht im, chuyn ng quay quanh mt trc , vch nn mt qu o trn tm O, bn knh R = 50 cm. Bit rng thi im t1 =1s cht im ta gc 1 = 30o; thi im t2 = 3s cht im ta gc 2 = 60o v n cha quay ht mt vng. Tc di trung bnh ca vt l: A. 6,5 cm/s B. 0,65 m/sC. 13 cm/s D. 1,3 m/s 17. Mt vt rn coi nh mt cht im chuyn ng trn qu o trn bn knh bng 40 m. qung ng i c trn qu o c cho bi cng thc : s = - t2 + 4t + 5 (m). Gia tc php tuyn ca cht im lc t = 1,5 s l:A. 0,1 cm/s2 B. 1 cm/s2 C. 10 cm/s2 D. 100 cm/s2 18.Mt vtchuynngtrnmtngtrnc ta gcph thucvothigiantvi biuthc:=2t2+3(rad;s).Khit=0,5stcdicavtbng2,4m/s.Giatcton phn ca vt l: A. 2,4 m/s2 B. 4,8 2m/s2 C. 4,8 m/s2D. 9,6 m/s2 19. Mt vt rn quay quanh mt trc c nh i qua vt c phng trnh chuyn ng: = 10 + t2 (rad; s). Tc gc v gc m vt quay c sau thi gian 5 s k t thi im t = 0 ln lt l: -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN10 A. 10 rad/s v 25 radB. 5 rad/s v 25 rad C. 10 rad/s v 35 rad D.5 rad/s v 35 rad 20. Bnh ca mt ng c t lc khi ng n lc t tc gc 140rad/s phi mt 2 s. Bit ng c quay nhanh dn u.Gc quay ca bnh trong thi gian l: A. 140rad. B. 70rad. C. 35rad. D. 36rad. 21. Mt bnh xe quay nhanh dn u quanh trc. Lc t = 0 bnh xe c tc gc 5rad/s. Sau 5s tc gc ca n tng ln 7rad/s. Gia tc gc ca bnh xe l: A. 0,2rad/s2. B. 0,4rad/s2. C. 2,4rad/s2. D. 0,8rad/s2. 22. Trong chuyn ng quay c vn tc gc v gia tc gc chuyn ng quay no sau y l nhanh dn? A. = 3 rad/s v = 0; B. = 3 rad/s v = - 0,5 rad/s2 C. = - 3 rad/s v = 0,5 rad/s2; D. = - 3 rad/s v = - 0,5 rad/s2 23. Mt bnh xe quay nhanh dn u t trng thi ng yn sau 2s n t tc gc 10rad/s. Gia tc gc ca bnh xe l A. 2,5 rad/s2;B. 5,0 rad/s2;C. 10,0 rad/s2; D. 12,5 rad/s2 24. Mt bnh xe c ng knh 4m quay vi gia tc gc khng i 4 rad/s2, t0 = 0 l lc bnh xe bt u quay. Ti thi im t = 2s tc gc ca bnh xe l: A. 4 rad/s.B. 8 rad/s. C. 9,6 rad/s. D. 16 rad/s. 25. Mt bnh xe c ng knh 4m quay vi gia tc gc khng i 4 rad/s2, t0 = 0 l lc bnh xe bt u quay. Tc dica mt im P trn vnh bnh xe thi im t = 2s l A. 16 m/s. B. 18 m/s.C. 20 m/s.D. 24 m/s. 26.Mtbnhxecngknh4mquayvigiatcgckhngi4rad/s2.Giatctip tuyn ca im P trn vnh bnh xe l A. 4 m/s2.B. 8 m/s2. C. 12 m/s2.D. 16 m/s2. 27. Mt bnh xe ang quay vi tc gc 36 rad/s th b hm li vi mt gia tc gc khng i c ln 3rad/s2. Thi gian t lc hm n lc bnh xe dng hn l A. 4s; B. 6s; C. 10s; D. 12s 28. Mt bnh xe ang quay vi tc gc 36rad/s th b hm li vi mt gia tc gc khng i c ln 3rad/s2. Gc quay c ca bnh xe k t lc hm n lc dng hn l A. 96 rad;B. 108 rad; C. 180 rad; D. 216 rad 29.Mtbnhxequaynhanhdnutrong4stcgctngt120vng/phtln 360vng/pht. Gia tc gc ca bnh xe l A. 2 rad/s2.B. 3 rad/s2. C. 4 rad/s2. D. 5 rad/s2. 30.Mtbnhxecngknh50cmquaynhanhdnutrong4stcgctngt 120vng/pht ln 360vng/pht. Gia tc hng tm ca im M vnh bnh xe sau khi tng tc c 2s l A.157,8 m/s2.B.162,7 m/s2. C.183,6 m/s2.D.196,5 m/s2 31. Mt bnh xe c ng knh 50cm quay nhanh dn u trong 4s tc gc tng t 120 vng/pht ln 360 vng/pht. Gia tc tip tuyn ca im M vnh bnh xe l: A. 0,25 m/s2; B. 0,50 m/s2; C. 0,75 m/s2; D. 1,00 m/s2 32. Mt bnh xe bt u quay nhanh dn u quanh mt trc c nh ca n. Sau 10 s k t lc bt u quay, vn tc gc bng 20 rad/s. Vn tc gc ca bnh xe sau 15 s k t lc bt u quay bng A. 15 rad/s. B. 20 rad/s.C. 30 rad/s.D. 10 rad/s. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN11 33. Ti thi im t = 0, mt vt rn bt u quay quanh mt trc c nh xuyn qua vt vi gia tc gc khng i. Sau 5 s n quay c mt gc 25 rad. Vn tc gc tc thi ca vt ti thi im t=5s l A. 5 rad/s. B. 10 rad/s.C. 15 rad/s. D. 25 rad/s. 34. Mt bnh xe ang quay vi tc gc 24 rad/s th b hm. Bnh xe quay chm dn u vi gia tc gc c ln 2 rad/s2. Thi gian t lc hm n lc bnh xe dng bng: A. 8 s. B. 12 s.C. 24 s. D. 16 s. 35.Mtvtrnquayquanhmttrccnhiquavtcphngtrnhchuynng =10+t2 (tnh bng rad, t tnh bng giy). Tc gc v gc m vt quay c sau thi gian 5 s k t thi im t = 0 ln lt l A. 5 rad/s v 25 rad B. 5 rad/s v 35 rad.C.10 rad/s v 35 rad. D.10 rad/s v 25 rad. 36. Phng trnh to gc theo thi gian t ca mt vt rn quay bin i c dng : = 2008+2009t +12 t2 (rad, s).Tnh tc gc thi im t = 2s A. = 2009 radB. = 4018 radC. = 2057 radD. = 2033 rad 37. Mt vt rn quay nhanh dn u quanh mt trc c nh, trong 3,14 s tc gc ca n tng t 120 vng/pht n 300 vng/pht. Ly = 3,14. Gia tc gc ca vt rn c ln lA. 6 rad/s2. B. 12 rad/s2. C. 8 rad/s2. D. 3 rad/s2. 38. Mt bnh xe quay nhanh dn u t trng thi ngh, sau 4s u tin n ttc gc 20rad/s. Tm gc quay ca bnh xe trong thi gian : A. 20rad B. 80rad C. 40radD. 160rad. 39. Mt bnh xe ang quay vi tc gc 0 th quay chm dn u, sau 2s th quay c mt gc 20rad v dng li. Tm 0 v gia tc gc A. 0= 20rad/s v = 10rad/s B. 0= 10rad/s v = 10rad/s C. 0= 20rad/s v = 5rad/sC. 0= 10rad/s v = 20rad/s. 40.Mt vt rn quay nhanh dn u quanh mt trc c nh vi phng trnh ta gc =t + t2 ( tnh bng rad, tnh bng s ). Vo thi im t = 1 s, mt im trn vt cch trc quay mt khong r = 10 cm c tc di bng: A.20 cm/s. B.30 cm/s.C.50 cm/s.D.40m/s. 41. Mt vt rn quay u quanh mt trc c nh vi phng trnh tc gc = 4t +2 ( tnh bng rad/s, t tnh bng s ). Gia tc tip tuyn ca mt im trn vt rn cch trc quay on 5 cm bngA.20 cm/s2.B.10 cm/s2.C.30cm/s2. D.40cm/s2 42. Ti mt thi im t = 0, mt vt bt u quay quanh mt trc c nh xuyn qua vt vi gia tc gc khng i. Sau 5 s, n quay mt gc 10 rad. Gc quay m vt quay c sau thi gian 10 s k t lc t = 0 bngA.10 rad. B.40 rad.C.20 rad.D.100 rad. 43. Mt a trn, phng, mng quay u quanh mt trc qua tm v vung gc vi mt a. Gi vA v vB ln lt l tc di ca im A vnh a v ca im B (thuc a) cch tm mt on bng na bn knh ca a. Biu thc lin h gia vA v vB lA. vA = vB.B. vA = 2vB. C. 2BAvv = D. vA = 4vB.44. T trng thi ngh, mt a bt u quay quanh trc c nh ca n vi gia tc gc khng i. Sau 10s, a quay c mt gc 50 rad. Gc m a quay c trong 10 s tip theo lA. 100 rad.B. 200 rad.C. 150 rad.D. 50 rad. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN12 45. Mt vt quay nhanh dn t trng thi ngh, trong giy th 4 vt quay c gc 14 rad. Hi trong giy th 3 vt quay c gc bao nhiu ?A. 10 rad B. 5 radC. 6 rad D.2 rad 46.Mt cnh qut ca mt pht in chy bng sc gi c ng knh 80m, quay vi tc 45vng/pht. Tc ca mt im nm vnh cnh qut l: A. 18,84 m/sB. 188,4 m/s C. 113 m/sD. 11304m/s CH 2: MOMEN NG NNG VT RN Phng php: Vn dng nh lut bo ton mmen ng lng. * Phng php gii: tm cc i lng lin quan n nh lut bo ton ng lng khi vt rn quay quanh mt trc ta vit cc biu thc lin quan n i lng cn tm v cc i lng bit t suy ra v tnh i lng cn tm. * Cc cng thc: + Momen ng lng: L = I. Vi cht im quay: I = mr2L = mr2 = mrv. + Dng khc ca phng trnh ng lc hc ca vt rn quay quanh mt trc c nh: M = dLdt. + nh lut bo ton momen ng lng: Nu M = 0 th L = const hay I11 + I12 + = I11 + I22 + Nu I = const th = 0: vt rn khng quay hoc quay u quanh trc. Nu I thay i th I11 = I22. I. TRC NGHIM L THUYT 47 Chn cu pht biu sai A. Mmen lc l i lng c trng cho tc dng lm quay ca lc. B.Mmen lc l i lng c trng cho tc dng lm quay ca vt. C.Mmen lc c o bng tch ca lc vi cnh tay n ca lc . D. Cnh tay n l khong cch t trc quay n gi ca lc. 48. Mt momen lc khng i tc dng vo mt vt c trc quay c nh. Trong nhng i lng di y, i lng no khng phi l hng s? A. Momen qun tnh.B. Khi lng. C. Gia tc gc.D. Tc gc.49. i vi vt quay quanh mt trc c nh, cu no sau y l ng? A. Nu khng chu momen lc tc dng th vt phi ng yn. B.Khi khng cn momen lc tc dng th vt ang quay s lp tc dng li. C.Vt quay c l nh c momen lc tc dng ln n. D. Khi thy tc gc ca vt thay i th chc chn c momen lc tc dng ln vt.50. Chn cm t thch hp vi phn trng trong cu sau:Mt vt rn c th quay c quanh mt trc c nh, mun cho vt trng thi cn bng th ..................... tc dng vo vt rn phi bng khng. A. hp lc B. tng cc momen lcC. ngu lc D. tng i s. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN13 51. Ngu lc l: A.hhailctcdnglnmtvt,bngnhauvln,songsong,ngcchiu,khng cng ng tc dng. B.hhailctcdnglnhaivt,bngnhauvln,songsong,ngcchiu,khng cng ng tc dng. C.hhailctcdnglnmtvt,bngnhauvln,songsong,cngchiu,khng cng ng tc dng. D.h hai lc tc dng ln hai vt, bng nhau v ln, song song, cng chiu, khng cng ng tc dng. 52. Mt ngu lc gm hai lc 1Fr v2Fr, c F1 = F2 = F v c cnh tay n d. M men ca ngu lc ny l: A. FdB. (F1 F2).d C. (F1 + F2).dD. Cha d liu tnh ton.53. Pht biu no sau y l ng khi ni v ngu lc? A. Mmen ca ngu lc khng c tc dng lm bin i vn tc gc ca vt. B. Hai lc ca mt ngu lc khng cn bng nhau. C. i vi vt rn khng c trc quay c nh, ngu lc khng lm quay vt. D. Hp lc ca mt ngu lc c gi i qua khi tm ca vt. 54. nh l v trc song song c mc ch dng :A. Xc nh momenng lng ca vt rn quay quanh mt trc i qua trng tm canB. Xc nh ng nng ca vt rn quay quanh mt trc i qua trng tm ca nC. Xc nh ng nng ca vt rn quay quanh mt trc khng i qua trng tm ca n D.Xcnhmomenquntnhcavtrnquayquanhmttrckhngiquakhi tm ca n55. Chn cu khng chnh xc: A. Mmen lc c trng cho t/dng lm quay vt ca lc B. Mmen lc bng 0 nu lc c phng qua trc quay C. Lc ln hn phi c m men lc ln hnD.Mmenlccthmcth dng 56. Pht biu no Sai khi ni v momen qun tnh ca vt rn i vi trc quay xc nh: A.Momenquntnhcavtrncctrngchomcquntnhcavttrongchuyn ng. B. Momen qun tnh ca vt rn ph thuc vo v tr trc quay. C. Momen qun tnh ca vt rn c th dng, c th m ty thuc vo chiu quay ca vt. D. Momen qun tnh ca vt rn lun lun dng 57. Khng nh no sau y l ng: A. Khi momen ng lng c bo ton th vt ng yn B. Khi ng nng c bo ton th vt trng thi cn bng C. Khi momen lc tc dng ln vt bng 0 th vt ng yn D. Khi vt chu tc dng ca cp lc ngc chiu, cng ln th vt ng yn 58. i lng vt l no c th tnh bng kg.m2/s2? A. Momen lc. B. Cng. C. Momen qun tnh. D. ng nng. 59. Mt cht im chuyn ng trn xung quanh mt trc c momen qun tnh i vi trc l I. Kt lun no sau y l khng ng?-T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN14 A. Tng khi lng ca cht im ln hai ln th mmen qun tnh tng ln hai ln B. Tng khong cch t cht im n trc quay ln hai ln th mmen qun tnh tng 2 ln C. Tng khong cch t cht im n trc quay ln hai ln th mmen qun tnh tng 4 lnD.Tngngthikhilngcachtimlnhailnvkhongcchtchtim n trc quay ln hai ln th mmen qun tnh tng 8 ln 60. Pht biu no sau y l khng ng?A. Momen qun tnh ca vt rn i vi mt trc quay ln th sc ca vt trong chuyn ng quay quanh trc ln. B. Momen qun tnh ca vt rn ph thuc vo v tr trc quay v s phn b khi lng i vi trc quay C. Momen lc tc dng vo vt rn lm thay i tc quay ca vtD. Momen lc dng tc dng vo vt rn lm cho vt quay nhanh dn 61. Phtbiunosaikhinivmomenquntnhcamtvtrnivimttrcquay xcnh? A. Momen qun tnh ca mt vt rn c th dng, c th m ty thuc vo chiu quay ca vt. B. Momen qun tnh ca mt vt rn ph thuc vo v tr trc quay.C. Momen qun tnh ca mt vt rn c trng cho mc qun tnh ca vt trong chuyn ng quay.D. Momen qun tnh ca mt vt rn lun lun dng. 62. Mt vt rn c momen qun tnh I i vi trc quay c nh i qua vt. Tng momen ca cc ngoi lc tc dng ln vt i vi trc l M . Gia tc gcm vt thu c di tc dng ca momen l: A.IM= == =2 B. MI= == =C. MI= == =2 D. IM= == = 63. Momen qun tnh ca mt vt rn i vi mt trc quay khng ph thuc vo:A. v tr ca trc quay .B. khi lng ca vt. C. vn tc gc (tc gc) ca vt.D. kch thc v hnh dng ca vt 64. i lng trong chuyn ng quay ca vt rn tng t nh khi lng chuyn ng ca cht im l: A. momen ng lng B. momen qun tnhC. momen lc D. tc gc. 65. Nu tng momen lc tc dng ln vt bng khng th:A.momen ng lng ca vt bin i u B. gia tc gc ca vt gim dnC.tc gc ca vt khng iD.gia tc gc ca vt khng i 66. Trong chuyn ng quay ca vt rn quanh mt trc c nh, momen qun tnh ca vt i vi trc quayA. t l momen lc tc dng vo vtB. t l vi gia tc gc ca vt C. ph thuc tc gc ca vtD. ph thuc v tr ca vt i vi trc quay 67. Cc vn ng vin nhy cu xung nc c ng tc "b gi" tht cht trn khng l nhmA. Gim mmen qun tnh tng tc quay; B.Tngmmenquntnhtng tc quay C. Gim mmen qun tnh tng mmen ng lng D.Tngmmenquntnh gim tc quay -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN15 68. Cc ngi sao c sinh ra t nhng khi kh ln quay chm v co dn th tch li do tc dng ca lc hp dn. Tc gc quay ca saoA. khng i; B. tng ln;C. gim i; D. bng khng 69. o hm theo thi gian ca momen ng lng ca vt rn i vi mt trc quay l mt hng s khc khng th vtA. chuyn ng quay u.B.quay nhanh dn u.C.quaychmdnu.D. quay bin i u. 70. Trong chuyn ng quay ca vt rn, i lng nh ng lng trong chuyn ng ca cht im l A. momen ng lng. B. momen qun tnh.C. momen lc.D. tc gc. 71.Phtbiunosauylkhngngkhinivmomennglngcavtrnquay quanh mt trc c nh? A. Momen ng lng lun cng du vi tc gcB.nvomomennglng l kgm2/s C. Momen ng lng ca vt rn t l vi tc gc ca n D. Nu tng cc lc tc dng ln vt rn bng khng th momen ng lng ca vt rn c bo ton 72. Phng trnh ng lc hc ca vt rn chuyn ng quanh mt trc c th vit di dng no sau y?A. M = I dtd B. M = dtdL C. M = I D. C A, B, C.73. Chn cu sai. A. Tch ca momen qun tnh ca mt vt rn v tc gc ca n l momen ng lng. B. Momen ng lng l i lng v hng, lun lun dng. C. Momen ng lng c n v l kgm2/s. D. Nu tng cc momen lc tc dng ln mt vt bng khng th momen ng lng ca vt c bo ton. 74. my bay ln thng, ngoi cnh qut ln pha trc cn c mt cnh qut nh pha ui. Cnh qut nh ny c tc dng g? A. Lm tng vn tc ca my bay. B.Gim sc cn khng kh tc dng ln my bay. C. Gi cho thn my bay khng quay. D. To lc nng nng pha ui.75. Trong chuyn ng quay ca vt rn, i lng nh khi lng trong chuyn ng ca cht im l A. momen ng lng.B. momen qun tnh.C. momen lc.D. tc gc. 76. Vi cng mt lc tc dng, cng phng tc dng, nu im t cng xa trc quay th tc dng lm vt quay A. cng mnhB. cng yu C. vn khng iD.cthcngmnh hoc cng yu 77. ng nng ca vtquay quanh mt trc c nh vi tc gc l : A.tng ln hai ln khi tc gc tng ln hai ln. B.gim bn ln khi momen qun tnh gim hai ln. C.tng ln chn ln khi momen qun tnh ca n i vi trc quay khng i v tc gc tng ba ln. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN16 D.ng nng ca vt gim i hai ln khi khi lng ca vt gim bn ln. 78. ng nng ca vt rn quay quanh mt trc bngA.tchscamomenquntnhcavtvbnhphngvntcgccavtivitrc quay .B. na tch s ca momen qun tnh ca vt v bnh phng vn tc gc ca vt i vi trc quay . C. na tch s ca momen qun tnh ca vt v vn tc gc ca vt i vi trc quay . D.tchscabnhphngmomenquntnhcavtvvntcgccavtivitrc quay . II. CC DNG BI TP : DNG 1: MOMEN QUN TNH MOMEN LC * Phng php gii: tm cc i lng lin quan n phng trnh ng lc hc ca vt rn quay quanh mt trc ta vit cc biu thc lin quan n i lng cn tm v cc i lng bit t suy ra v tnh i lng cn tm. * Cc cng thc: + Momen lc: M = Fd. + Momen qun tnh ca cht im v ca vt rn quay: I = mr2 v I = 2i iimr. +MomenquntnhIcamtsvtrnngchtkhilngmctrcquayltrci xng: - Thanh c chiu di l, tit din nh so vi chiu di: I = 112ml2. - Vnh trn hoc tr rng, bn knh R: I = mR2. - a trn mng hoc hnh tr c, bn knh R: I = 12mR2. - Hnh cu rng, bn knh R: I = 23mR2. - Khi cu c, bn knh R: I = 25mR2. + Thanh ng cht, khi lng m, chiu di l vi trc quay i qua u mt ca thanh:I = 13ml2. + Phng trnh ng lc hc ca vt rn quay quanh mt trc c nh: M = I. * V D minh ha: VD1.Mtthanhcngngchtcchiudil,khilngm,quayquanhmttrcqua trungimvvunggcvithanh.Chomomenquntnhcathanhivitrcl 21m12l . Gn cht im c khi lng m3 vo mt u thanh. Tnhmomen qun tnh ca h i vi trc . HD: Ta c: I = I1 + I2 = 21m12l+ m3(2l)2 = 21m6l . -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN17 VD2. Mt a trn ng cht c khi lng m = 20 kg, bn knh R = 20 cm, trc quay l trc i xng. Khi a ang ng yn, tc dng vo n mt lc c momen M = 10 Nm. Tnh tc gc ca a sau 5 s k t lc tc dng momen lc vo a. HD: 2. Ta c: I = 12mR2 = 0,4 kgm2; = MI = 25 rad/s2; = 0 + t = 125 rad/s. V3.Mtbnh l mtkhi tr c, ngcht,khilng 5 kg,bnknh 10cmang trngthinghctrcquaytrngvitrccahnhtr.Ngitatcdngvonmt momen lc c ln 7,5 Nm. Tnh gc quay c ca bnh sau 10 s. HD: Ta c I = 12mR2 = 0,001 kgm2; = MI = 20 rad/s2; = 12 t2 = 160 rad.; s = R = 16 m. VD4. Mt a c ng cht khi lng 0,2 kg, bn knh 10 cm, c trc quay i qua tm a vvunggcvia.aangngynthngitatcdngvoamtmomenlc khng i 0,02 Nm. Tnh qung ng m mt im trn vnh a i c sau 4 s k t lc tc dng momen lc. HD:Ta c I = 12mR2 = 0,025 kgm2; = MI = 300 rad/s2; = 12 t2 = 15000 rad. VD5.Mtatrnphng,ngchtckhilngm=2kgvbnknhR=0,5m.Bit momen qun tnh i vi trc qua tm i xng v vung gc vi mt phng a l 12mR2. T trng thi ngh, a bt u quay xung quanh trc c nh, di tc dng ca mt lc tip tuyn vi mp ngoi v ng phng vi a. B qua cc lc cn. Sau 3 s a quay c mt gc 36 rad. Tnh ln ca lc ny. HD: Ta c: =0t + 12 t2 =12 t2 (v 0= 0) = 22t = 8 rad/s2.V M = FR = IF = IR = 21RR22mmR== 4 N. VD6. Mt vt rn ang quay u quanh trc c nh vi tc gc 30 rad/s th chu tc dngcamtmomenhmclnkhnginnquaychmdnuvdnglisau2 pht. Bit momen ca vt rn ny i vi trc l 10 kg.m2. Tnh ln momen hm. HD: Ta c: = 00t t = - 0,25 rad/s2; |M| = I|| = 2,5 Nm. VD7. Mt qu cu c, ng cht bn knh 20 cm ang quay u quanh trc i xng ca n vi tc 3000 vng/pht. Tc dng mt momen hm khng i c ln 100 Nm vo qu cu th n quay chm dn u v dng li sau 5 s. Tnh khi lng ca qu cu. HD: Ta c: = 00t t = 0 50.25 0 = - 20 (rad/s2); |M| = I|| = 25mR2 ||m = 25| |2R | |M = 99,5 kg. VD8.Mtcigumcnckhilng5kgcthxunggingnhmtsidydi qun quanh mt hnh tr c bn knh R = 20 cm v momen qun tnh I = 1,8 kgm2. B qua -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN18 khi lng ca dy v ma st khi hnh tr quay quanh trc i xng ca n. Ly g = 10 m/s2. Tnh gia tc ca gu khi th xung. HD: Ta c: M = TR = I = IaRT = 2IaR. Mt khc: mg T = mamg - 2IaR = maa = 2mgImR+ = 1 m/s2. VD9. Vnh trn c khi lng m, bn knh R, momen qun tnh i vi trc i xng i qua tm ca vnh trn l I = mR2, ln khng trt trn mt phng nghing c gc nghing = 300. Ly g = 10 m/s2. B qua lc ma st ln. Tnh gia tc ca tm vnh trn. HD : Vnh trn va chuyn ng tnh tin va chuyn ng quay v v b qua ma st ln nn y ch cn ma st ngh. Vi chuyn ng tnh tin, ta c: ma = mgsin - Fms (1). Vi trc quay i qua tm O, ta c: MFms + MP + MN = I = mR2.aR = maR. VP vN c gi i qua O nn MP = 0; MN = 0 v MFms = FmsRFms = ma(2). T (1) v (2) suy ra: a = sin2g = 2,5 m/s2. * TRC NGHIM TNG HP 79. Tc dng mt mmen lc M = 0,32 N.m lnmt cht im chuyn ng trn mt ng trn lm cht im chuyn ng vi gia tc gc khng i = 2,5rad/s2. Mmen qun tnh ca cht im i vi trc i qua tm v vung gc vi ng trn l: A. 0,128 kg.m2 B. 0,214 kg.m2 C. 0,315 kg.m2 D.0,412 kg.m2 80. Mt ci bp bnh trong cng vin c chiu di 2 m, c trc quay nm trung im I ca bp bnh. Hai ngi c khi lng ln lt l m1 = 50 kg v m2 = 70 kg ngi hai u bp bnh. Ly g = 10 m/s2. M men lc i vi trc quay ca bp bnh bng : A. 200 N.mB. 500 N.mC. 700 N.m D. 1200 N.m 81. Mt a mng, phng, ng cht c bn knh 2m c th quay c xung quanh mt trc iquatmvvunggcvimtphnga.Tcdngvoamtmmenlc960N.m khng i, a chuyn ng quay quanh trc vi gia tc gc 3rad/s2. Khi lng ca a l A. m = 960 kg B. m = 240 kgC. m = 160 kg D.m= 80 kg 82. Mt rng rc c bn knh 10cm, c mmen qun tnh i vi trc l I =10-2 kgm2. Ban u rng rc ang ng yn, tc dng vo rng rc mt lc khng i F = 2N tip tuyn vi vnh ngoi ca n. Gia tc gc ca rng rc l A. 14 rad/s2B. 20 rad/s2 C. 28 rad/s2 D. 35 rad/s2 83. Mt rng rc c bn knh 10cm, c mmen qun tnh i vi trc l I =10-2 kgm2. Ban u rng rc ang ng yn, tc dng vo rng rc mt lc khng i F = 2N tip tuyn vi vnh ngoi ca n. Sau khi vt chu tc dng lc c 3s th tc gc ca n l A. 60 rad/s B. 40 rad/sC. 30 rad/s;D. 20rad/s 84. Mt bnh xe c momen qun tnh i vi trc quay c nh l 6kg.m2, ang ng yn th chu tc dng ca momen lc 30N.m i vi trc quay. Sau bao lu, k t khi bt u quay bnh xe t ti tc gc 100rad/s A. 10sB. 15s C. 20sD. 25s. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN19 85. Mt ci a c momen qun tnh i vi trc quay l 1,2kg.m2. a chu mt momen lc khngi16N.m,sau33sktkhikhingaquaycmtgc: A. 7260rad B. 220radC. 440rad D. 14520rad. 86. Hai cht im c khi lng 0,2kg v 0,3kg gn hai u mt thanh cng, nh, c chiu di 1,2m. Momen qun tnh ca h i vi trc quay i qua trung im ca thanh v vung gcvithanhcgitrnosauy? A. 1,58kg.m2 B. 0,18kg.m2 C. 0,09kg.m2 D. 0,36kg.m2. 87. Mt thanh mng AB c khi lng M = 1kg, chiu di l = 2m, hai u thanh gn hai cht imc khilng bng nhaulm=100g. Momenqun tnhca h i vi trcquayi qua trung im ca thanh v vung gc vi thanh c gi tr no sau y?A. 0,53kg.m2 B. 0,64kg.m2 C. 1,24kg.m2 D. 0,88kg.m2 88. Hai rng rc A v B c khi lng ln lt l m v 4m, bn knh ca rng rc A bng 1/3bnknhrngrcB.TlIA/IBgiamomenquntnhcarngrcAvrngrcB bng: A. 4/3 B. 9 C. 1/12 D. 1/36 89. Mt vt rn ang quay u quanh trc c nh vi tc gc 30 rad/s th chu tc dng camtmomenhmclnkhnginnquaychmdnuv dng lisau2pht. Bit momen qun tnh ca vt rn ny i vi trc quay l 10 kg.m2. Momen hm c ln bng: A. 2,0 Nm.B. 2,5 Nm.C. 3,0 Nm.D. 3,5 Nm. 90. Mt hnh tr rng c khi lng 0,2kg c th quay quanh mt trc nm ngang. Vt qua hnh tr ny mt on dy khng dn, khi lng khng ng k, hai u treo hai vt nng khi lng m1 = 0,8kg v m2 = 0,5kg. Ly g = 10m/s2. Th cho cc vt chuyn ng th sc cng dy hai on dy treo hai vt ln lt l: A. T1=8,6N; T2 = 4,2N B. T1=6,4N; T2 = 4,2N C. T1=8,6N; T2 = 6,0N D. T1=6,4N; T2 = 6,0N 91. Mt rng rc c hai rnh vi bn knh ln lt l R1 v R2 m R1 = 2R2. Mi rnh c mt dykhngdnqun vo,utdomangvt nng hnhv.Thchoccvtchuynng. Bit qia tc ca vt m1 l a1 = 2m/s2 th gia tc ca vt m2 l: A. 1 m/s2B.4m/s2C. 2m/s2D. 8m/s2 92. Mt lc 10 N tc dng theo phng tip tuyn vi vnh ngoi ca mt bnh xe c bn knh40cm.Bnhxequayttrngthinghvsau1,5sthquayc1vngutin. Momen qun tnh ca bnh xe l A. I = 0,96 kg.m2.B. I = 0,72 kg.m2.C. I = 1,8 kg.m2.D. I = 4,5 kg.m2. 93.Mtmomenlckhngi30N.mtcdngvomtbnhcmomenquntnh12 kg.m2. Thi gian cn thit bnh t ti tc gc 75 rad/s t trng thi ngh l A. t = 180 s. B. t = 30 s.C. t = 25 s.D. t = 15 s. 94. C 4 cht im, khi lng mi cht im l m, c t 4 nh hnh vung cnh l a. Momen qun tnh ca h thng 4 cht im y i vi trc quay qua tm v vung gc vi hnhvungcgitr A. 4ma2B. 2ma2 C. ma2 D. ma2/2. 95. Mt a trn ng cht khi lng m=1kg, bn knh R=20cm ang quay u quanh mt trc qua tm a v vung gc vi mt a vi tc gc 0=10rad/s. Tc dng ln a mt -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN20 momen hm, a quay chm dn v sau khi quay c mt gc 10rad th dng li. Momen hm c gi tr: A. 0,2N.m B. 0,5N.mC.0,3N.m D. 0,1N.m. 96. Mt tam gic u c cnh l a. Ba cht im, mi cht im c khi lng l m, c t ba nh ca tam gic. Momen qun tnh ca h ny i vi trc quay l mt ng cao ca tam gic bng: A.ma2/2 B.ma2/4C.3ma2/2 D.3ma2/4. 97. Mt a trn phng, ng cht c khi lng m = 2 kg v bn knh R = 0,5 m.T trng thi ngh, a bt u quay xung quanh trc c nh qua tm a. Di tc dng ca mt lc tip tuyn vimp ngoi v ng phng vi a. B qua cc lc cn. Sau 3 s a quay c 36 rad. ln ca lc ny l:A. 6N.B. 3N. C. 4N.D. 2N. 98.Mtthanhcngngchtcchiudi,khilngm,quayquanhmttrcqua trungimvvunggcvi thanh.Gn chtimckhilng3mvomtuthanh. Momen qun tnh ca h i vi trc lA. 1213m2.B. 31m2.C. 34m2. D. 65m2. 99. Mt vt nng 60N c buc vo u mt si dy nh qun quanh mt rng rc c c khi lng 4kg, ly g= 10m/s2.Rng rc c trc quay c nh nm ngang v i qua tm ca n. Vt c th t trng thi ngh th gia tc ca vt l (b qua ma st, dy khng dn): A. 6m/s2 B. 7,5m/s2 C. 8m/s2D. 9m/s2 100. Mt bnh xe c bn knh R = 5cm b tc dng bi hai lc 1Fr v 2Fr c im t ti A v Btrnvnh bnhxe nh hnh vvi 110 2 F = N, 220 3 F = N.lncamomen lc tng hp i vi trc quay O do hai lc gy ra l: A. 5N.mB. 15N.m C. 8N.mD. 10N.m 101. Di tc dng ca lc nh hnh v. Mmen lc lm cho xe quay quanh trc ca bnh xe theo chiu no v c ln bng bao nhiu? A.Cng chiu kim ng h, ln M = 1 N.m. B.Ngc chiu kim ng h, ln M = 5 N.m. C.Cng chiu kim ng h, ln M = 40 N.m. D.Cng chiu kim ng h, ln M = 60 N.m.102.Dngmtrngrccnhcdngmtaphngtrnckhilngkhng ngk,cbnknhR=50cm.Dngmtsidykhngcodnckhilng khng ng k vt qua rng rc. Hai u dy treo hai vt khi lng m1 = 2 kg, m2 = 5 kg nh hnh v. Ly g = 10 m/s2. M men lc tc dng ln rng rc l: A. 10 N.m B. 15 N.mC. 25 N.mD. 35 N.m 103. Xt mt h thng nh hnh v. Rng rc l mt a trn c khi lng m = 1kg cthquaykhngmastxungquanhtrcquaO.DyABvtquarngrc(khilng khng ng k v khng co dn). Vt nng khi lng 2kg treo u dy A. LcFr hng thngngxungditcdnguBcadykovtAlnviF=25N.Lyg= 10m/s2. Gia tc a ca vt nng v lc cng dy T: A. a = 1m/s2; T = 24N B. a = 1m/s2; T = 12N C.a=2m/s2;T=12N D. a = 2m/s2; T = 24N 1 2 -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN21 104. Mt rng rc c bn knh R = 20cm,momen qun tnh i vi trc quay O l I = 0,5 kg.m2.Vtquarngrcmtondynh,khngdn,haiudyckobihailc 1 2, F Fr r cng phng thng ng v hng xung nh hnh v, c ln F1 = 5N, F2 = 10N. Gia tc tip tuyn ca mt im trn vnh rng rc l: A. 0,5m/s2B. 0,4m/s2C. 1 m/s2D. 2 m/s2 105. Mt hnh tr c c khi lng 500g c th quay quanh mt trc nh hnh v. Mt dy c qun vo hnh tr, u dy mang vt nng khi lng 250g. B qua khi lng dy v ma st trc. Ly g= 10 m/s2. Th vt n chuyn ng. Sc cng ca dy l: A. 1,25NB. 1,5NC. 2N D. 2,5N 106. O l rng rc c nh. Ta dng lc F = 4N ko u mt dy vt qua rng rc nng vt c khi lng m = 300g. Bit rng rc c bn knh R = 20cm v momen qun tnh i vi trc quay O l I = 0,068kg.m2. Ly g = 10m/s2. Gia tc gc ca rng rc l: A. 3 rad/s2B. 2,5 rad/s2C. 1,8 rad/s2 D. 1,5 rad/s2 107. Rng rc l mt a trn ng cht c khi lng 400g. Si dy mnh, khng dn vt qua rngrc, hai u hai u dy c treo hai vt nng khi lng ln lt l 500g v 300g. Ly g = 10m/s2. Sau khi th cho h hai vt nng chuyn ng th gia tc ca chng c ln l: A. 1m/s2 B. 2m/s2C. 1,5m/s2D. 2,5m/s2 108. Xt mt h thng gm: rng rc l mt a trn c khi lng 100g, mt si dy khng dn v khi lng khng ng k vt qua rng rc, hai vt nng A v B khi lng ln lt m1 = 300g v m2 = 150g treo hai u dy. Ly g = 10m/s2. Th cho h chuyn ng khng vn tc u. Qung ng i c ca mi vt sau thi gian 4s k t lc th l: A. 24m B. 12mC. 20mD.Mtps khc P N 108 CU TRC NGHIM 1 C2B3B4A5D6A7D8C9A10D 11 A12A13C14A15C16C17C18B19A20A 21 B22D23B24B25A26B27D28D29A30A 31B32C33B34B35D36C37A38C39A40B 41A42 B43B44C45A46B47B48D49D50B 51A52C53B54D55C56D57B58A59B60D 61A62B63C64B65C66D67A68B69D70A -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN22 71D 72D73B74C75B76A77C78B79A80A 81C82B83A84C85A86B87A88D89B90D 91A92B 93B 94B95D96A97C98D99B100D 101D102B103D104B105A106B107B108A DNG 2: MOMEN NG LNG * KIN THC CHUNG: - L i lng ng hc c trng cho chuyn ng quay ca vt rn quanh mt trc: = L I(kg.m2/s) - Lu : Vi cht im th mmen ng lng2L mrmvr = = (rlkhongccht vr n trc quay) - Momen ng lng ca h vt: 1 2... L L L = + +L l i lng i s - bin thin momen ng lng: . L M t = * Bi tp minh ha: VD1. Mt thanh ng cht c khi lng 1,5 kg, di 160 cm quay u quanh trc i xng vung gc vi thanh vi tc gc 20 rad/s. Tnh momen ng lng ca thanh i vi trc quay . HD: Ta c: I = 112ml2 = 0,32 kgm2; L = I = 6,4 kgm2/s. VD2. Mt sn quay hnh tr c c khi lng m1 = 100 kg, bn knh R = 1,5 m, mp sn c mt vt khi lng m2 = 50 kg. Sn quay u quanh trc i xng ca n vi tc gc = 10 rad/s. Tnh momen ng lng ca h. HD. Ta c: I = I1 + I2 = 12m1R2 + m2 R2 = 225 kgm2; L = I = 2250 kgm2/s. VD3. Coi Tri t l mt qu cu ng cht c khi lng m = 6,0.1024 kg, bn knh R = 6400 km Ly = 3,14. Tri t quay quanh trc vi chu k 24 gi. Tnh momen ng lng ca Tri t trong chuyn ng quay xung quanh trc ca n. HD Ta c: = 2T = 7,27.10-5 rad/s; L = I = 22mR5 = 7145.1030 kgm2/s. 4. Mt thanh ng cht tit din nh khi lng 1,2 kg, di 1,6 m quay u quanh trc i qua trung trc ca thanh. Hai u thanh c gn hai cht im c khi lng m1 = 2 kg v m2 = 2 kg. Bit tc di ca mi cht im l 18 km/h. Tnh momen ng lng ca h. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN23 HD Ta c: L = I = (112ml2 + m1(2l)2 + m2(2l)2)12vl = 21,6 kgm2/s. 5. Mt ngi khi lng m = 50 kg ng mp ca mt sn quay tr chi. Sn c ng knh R = 3 m, momen qun tnh ca sn i vi trc quay i qua tm i xng ca sn l I = 2700 kgm2. Ban u sn ng yn. Khi ngi chy quanh sn vi tc v = 4 m/s (so vi sn) th sn cng bt u quay theo chiu ngc li. Tnh tc gc ca sn. HD. Theo nh lut bo ton ng lng ta c: I + mR2 + mR2vR = 0 = - 2mRvI mR += - 0,19 rad/s. VD6. Mt sn quay bn knh R = 2 m, momen qun tnh i vi trc quay qua tm sn l I = 800 kgm2. Khi sn ang ng yn, mt ngi c khi lng m1 = 50 kg ng mp sn nm vinckhilngm2=500g vi vntcv=25m/stheophngtip tuynvisn. Tnh vn tc ca ngi ngay sau khi nm. HD.Theonhlutbotonnglngtac:I+m1R2+m2R2vR=0=- 221m RvI m R += - 0,025 rad/s; v = R = - 0,05 m/s. VD7.Haiatrncmomenquntnh lnltlI15.10-2 kgm2vI2=3.10-2 kgm2ang quay ng trc v cng chiu vi tc gc1 = 10 rad/s v2 = 20 rad/s. Ma st trc quay nh khng ng k. Sau cho hai a dnh vo nhau v cng quay vi tc gc . Tnh . HD. Theo nh lut bo ton ng lng ta c: I11 + I22 = (I1 + I2) = 1 1 1 21 2I II I ++ = 13,75 rad/s. * TRC NGHIM TNG HP: 1.Mtthanhnhdi1mquayutrongmtphngngangxungquanhtrcthngngi qua trung im ca thanh. Hai u thanh c hai cht im c khi lng 2kg v 3kg. Tc dica mi cht im l 5m/s. Mmen ng lng ca thanh l: A. L = 7,5 kg.m2/sB. L = 10,0 kg.m2/s C. L = 12,5 kg.m2/sD. L = 15,0 kg.m2/s 2. Coi tri t l mt qu cu ng tnh c khi lng m = 6.1024kg, bn knh R = 6400 km. Mmen ng lng ca tri t trong s quay quanh trc ca n l: A. 5,18.1030 kg.m2/sB. 5,83.1031 kg.m2/sC. 6,28.1032 kg.m2/s D. 7,15.1033 kg.m2/s 3. Mt a c c bn knh 0,25m, a c th quay xung quanh trc i xng i qua tm v vung gc vi mt phng a. a chu tc dng ca mt momen lc khng i M = 3N.m.Mmen ng lng ca a ti thi im t = 2s k t khi a bt u quay l A. 2 kg.m2/sB. 4 kg.m2/sC. 6 kg.m2/s D. 7 kg.m2/s -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN24 4. Mt ci a trn bn knh R=2m, khi lng 4kg quay u vi tc d gc =6rad/s quanh mttrcthngngiquatma.Momennglngcaaivitrcquayl: A. 48kg.m2/sB. 96kg.m2/s C. 24kg.m2/s D. 52kg.m2/s. 5. Mt vt c mmen qun tnh 0,72 kg.m2 quay u 10 vng trong 1,8s. momen ng lng ca vt c ln l:A. 4,5 kg.m2/sB. 8,2 kg.m2/s C.13,24 kg.m2/sD. 25,12 kg.m2/s 6. Hai cht im chuyn ng quay quanh trc O vi m1 = 1kg; v1 = 3m/s; r1 = 50cm v m2 = 1,5kg; v2 = 2m/s; r2 = 30cm. ln momen ng lng ton phn ca hai cht im i vi trc qua O (vung gc vi mt phng hnh v) l: A. 0,6 kg.m2/sB. 1,2 kg.m2/s C. 1,8 kg.m2/sD. 0,3 kg.m2/s P N 6 CU: 1C; 2D; 3C; 4A; 5D; 6A DNG 3: NH LUT BO TON MOMEN NG LNG * Phng php gii: tm cc i lng lin quan n nh lut bo ton ng lng khi vt rn quay quanh mt trc ta vit cc biu thc lin quan n i lng cn tm v cc i lng bit t suy ra v tnh i lng cn tm. * Cc cng thc: + Momen ng lng: L = I. Vi cht im quay: I = mr2L = mr2 = mrv. + Dng khc ca phng trnh ng lc hc ca vt rn quay quanh mt trc c nh: M = dLdt. + nh lut bo ton momen ng lng: Nu M = 0 th L = const hay I11 + I12 + = I11 + I22 + Nu I = const th = 0: vt rn khng quay hoc quay u quanh trc. Nu I thay i th I11 = I22. * TRC NGHIM TNG HP 1.Mt ngi ckhi lngm=50kgngmp sn quay hnh tr ng knh 4m,c khi lng M = 200 kg. B qua ma st trc quay. Lc u h ng yn v xem ngi nh cht im. Ngi bt u chuyn ng vi vn tc 5 m/s (so vi t) quanh mp sn. Tc gc ca sn khi l : A. = 1,5 rad/s.B. = 1,75 rad/s.C. = -1,25 rad/s.D. = -0,625 rad/s. 2.Mtbntrnphngnmngangbnknh0,5mctrcquaycnhthngngi qua tm bn. Momen qun tnh ca bn i vi trc quay ny l 2 kg.m2. Bn ang quay u vi tc 2,05 rad/s th ngi ta t nh mt vt nh khi lng 0,2 kg vo mp bn v vt dnh cht vo . B qua ma st trc quay v sc cn ca mi trng. Tc gc ca h l A. = 2 rad/s.B. = 2,05 rad/s.C. = 1 rad/s.D.=0,25 rad/s. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN25 3.Mtngingcnhtrnmtbnxoayangquay,taycmhaiqut,miquc khi lng 5kg. Lc u hai tay ngi ny dang thng ra cho hai qu t cch trc quay 0,8m, khi bn quay vi tc 1= 2 vng/s. Sau ngi ny h tay xung hai qu t cch trc quay 0,2m th bn quay vi tc gc 2 . Cho bit momen qun tnh ca ngi v ban xoay i vi trc quay l khng i v bng 2kg.m2. Tnh 2 ? A. 3,5 vng/sB. 5 vng/sC. 7 vng/sD. 10 vng/s 4. Mt thanh OA ng cht v tit din u, chiu di l = 1m, khi lng 120g gn vung gc vi trc quay (D) thng ng. Trn thanh c mt vin boi nh khi lng 120g. Lc u vin bi khi tm G ca thanh v thanh quay vi tc gc 1= 120 vng/pht nhng sau vin bi c dch chuyn n u A ca th thanh quay vi tc gc l: A. 121,3 vng/phtB. 52,5 vng/phtC. 26,4 vng/phtD. 88,4 vng/pht P N 4 CU: 1C; 2A; 3C; 4B DNG 4: NG NNG CA VT RN * Phng php gii: tm cc i lng lin quan n ng nng v nh l bin thin ng nng ca vt rn quay quanh mt trc ta vit cc biu thc lin quan n i lng cn tm v cc i lng bit t suy ra v tnh i lng cn tm. * Cc cng thc: + ng nng ca vt rn quay: W = 12I2. + nh l bin thin ng nng ca vt rn quay: W = W2 - W1 = 12I22 - 12I21= A * V DMINH HA: VD1.Mtbnhcmomenquntnhivitrcquaycnhcanl0,4kg.m2. bnh tng tc t trng thi ng yn n tc gc phi tn cng 2000 J. B qua ma st. Tnh . HD.. Theo nh l bin thin ng nng ta c: 12I22 - 12I21= A. V 1 = 0 = 2AI = 100 rad/s. VD2. Mt momen lc 30 Nm tc dng ln mt bnh xe c momen qun tnh 2 kgm2. Bnh xe bt u quay t trng thi ngh. Tnh ng nng ca bnh xe sau 10 s k t lc bnh xe chu tc dng ca momen lc. HD.Ta c: = MI= 15 rad/s2; = 0 + t = 150 rad/s; W = 12I2 = 22500 J. VD3. Mt bnh quay nhanh dn u t trng thi ngh v sau 5 s th c tc gc 200 rad/s v c ng nng quay l 60 kJ. Tnh gia tc gc v momen qun tnh ca bnh i vi trc quay. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN26 3. Ta c: = 0t = 40 rad/s2; I = d22W = 3 kgm2. VD4. Tri t coi nh l hnh cu c khi lng 6.1024 kg, bn knh 6400 km, t quay quanh trc i xng ca n vi chu k 24 gi. Tnh ng nng ca Tri t trong chuyn ng t quay ny. HD.Ta c: I = 25mR2 = 98304.1034 kgm2; = 2T = 7,27.10-5 rad/s; W = 12I2 = 2,6.1030 J. VD5. Mt thanh ng cht, tit din u, khi lng 0,2 kg, di 0,5 m quay u quanh mt trcthngngiquatrungimcathanhvvunggcvithanhvitc120 vng/pht. Tnh ng nng ca thanh. HD:Ta c: W = 12I2 = 12112ml22 = 0,329 J. VD6. Mt qu cu c ng cht khi lng 0,5 kg quay xung quanh trc i qua tm ca n vi ng nng 0,4 J v tc gc 20 rad/s. Tnh bn knh ca qu cu. HD. Ta c: W = 12I2 = 1225m R22R = 25dWm = 0,1 m. VD7. Mt qu cu kim loi rng c ng knh 60 cm, khi lng 50 kg, c xem l phn b u trn b mt qu cu v c th quay quanh trc i xng i qua tm ca n. Tnh cng cn cung cp qu cu ang ng yn quay nhanh dn cho n khi t c vn tc 300 vng/pht. HD: Ta c: 12I22 - 12I21= A. V 1 = 0 v I = 23mR2A = 1223mR222 = 1480 J. VD8. Mt bnh c dng khi tr c khi lng 100 kg, bn knh 50 cm quay quanh trc i xng ca n. Trong thi gian tng tc, phng trnh ta gc ca mt im trn vnh bnh cdng: =3t2 + 8t + 4; trong tnhbngrad, ttnhbng s.Tnhcng thc hin ln bnh trong khong thi gian t t1 = 7 s n t2 = 12 s. HD Ta c: I = 12mR2 = 12,5 kgm2; so viphng trnh = 0 + 0t + 12 t2 th 0 = 8 rad/s v = 6 rad/s2; do : 1 = 0 + t1 = 50 rad/s; 2 = 0 + t2 = 80 rad/s; A = 12I22 - 12I21= 24375 J. * TRC NGHIM TNG HP 1.Mtbnhcmomenquntnh2,5kg.m2quayvitcgc8900rad/s.ngnng ca bnh bng:A. 9,1.108J.B. 11 125J. C. 9,9.107J.D.22 250J. 2. Mt ci ng hnh tr rng, ng cht c bn knh R v khi lng m ln u trn sn. Hy so snh ng nng tnh tin ca khi tm v ng nng quay ca ng quanh trc. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN27 A. W(tt) = 2W(quay)B. W(tt) = 12W(quay) C. W(tt) = W(quay) D. W(tt) = 4W(quay) 3. Mt khi hnh tr ng cht bn knh R, khi lng m = 2 kg, ln khng trt trn mt t vi tc v = 1 m/s. ng nng ca n l: A. 1 JB. 1,5 JC. 3 J D. 12 J 4. Mt cnh qut c momen qun tnh i vi trc quay c nh l 0,3 kg.m2, c tng tc t trng thi ngh n tc gc = 20 rad/s. Cn phi thc hin mt cng l: A. 60 JB. 120 JC. 600 JD. 1200 J 5. Hai a trn c cng momen qun tnh i vi cng mt trc quay i qua tm ca cc a. Lc u a 2 ( bn trn) ng yn, a 1 quay vi tc gc khng i 0. Ma st trc quay nh khng ng k. Sau cho hai a dnh vo nhau, h quay vi tc gc . ng nng ca h hai a lc sau tng hay gim so vi lc u? A. Tng 3 ln. B. Gim 4 ln. C. Tng 9 ln. D.Gim 2 ln. 6. Hai bnh xe A v B c cng ng nng quay, tc gc A = 3B. t s momen qun tnh IB/IA i vi trc quay i qua tm A v B nhn gi tr no sau y? A. 3 B. 9 C. 6 D. 1 7. Mt bnh xe c mmen qun tnh i vi trc quay c nh l 12kg.m2 quay u vi tc 30vng/pht. ng nng ca bnh xe l A. 360,0J B. 236,8J C. 180,0J D. 59,20J 8. Mt momen lc c ln 30Nm tc dng vo mt bnh xe c mmen qun tnh i vi trc bnh xe l 2kgm2. Nu bnh xe quay nhanh dn u t trng thi ngh th ng nng ca bnh xe thi im t = 10s l: A. 18,3 kJ B. 20,2 kJ C. 22,5 kJ D. 24,6 kJ 9. Mt sn quay hnh tr c khi lng 120 kg v c bn knh 1,5m. Sn bt u quay nh mt lc khng i, nm ngang, c ln 40N tc dng vo sn theo phng tip tuyn vi mp sn. ng nng ca sn sau 5s l:A. 653,4JB. 594JC. 333,3JD. 163,25J 10. Bit momen qun tnh ca mt bnh xe i vi trc ca n l 10kg.m2. Bnh xe quay vi vn tc gc khng i l 600 vng/pht (cho 2 = 10). ng nng ca bnh xe s l A. 6.280 J B. 3.140 JC. 4.103 JD. 2.104 J 11. Mt khi cu c khi lng M, bn knh R ln khng trt. Lc khi cu c vn tc v/2th biu thc ng nng ca n l A. 223Mv B. 232MvC. 257Mv D. 2407Mv 12. Mt bnh c momen qun tnh i vi trc quay c nh ca n l 0,4 kg.m2. bnh tng tc t trng thi ng yn n tc gc phi tn cng 2000 J. B qua ma st. Gi tr ca lA. 100 rad/s.B. 50 rad/s.C. 200 rad/s.D.10 rad/s. 13.Mtthanhmnhngchttitdinukhilngm,chiudil,cthquayquanh trc nm ngang i qua mt u thanh v vung gc vi thanh. B qua ma st trc quay v -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN28 sc cn ca mi trng. Momen qun tnh ca thanh i vi trc quay l 231ml I =v gia tc ritdolg.Nuthanhcthkhngvntcutvtrnmngangthkhitivtr thng ng thanh c tc gc bng A. lg3.B. lg23.C. lg32.D. lg 3. 14. Mt thanh OA ng cht, tit din u, khi lng m, chiu di l = 30cm, c th quay d dng trong mt phng thng ng xung quanh trc nm ngang u O. Lc u thanh ng yn v tr thng ng, ta truyn cho u A mt vn tcvr theo phng nm ngang. Ly g = 10m/s2. Vn tc ti thiu thanh quay n v tr nm ngang l: A. 3m/sB5m/sC. 10m/sD. 2m/s P N 14 CU: 1C; 2C; 3B; 4C; 5B; 6C; 7D ;8C 9C 10D 11B 12A 12A 13D 14A H v tn hc sinh :Trng I. KIN THC CHUNG:* Dao ng c, dao ng tun hon + Dao ng c l chuyn ng qua li ca vt quanh 1 v tr cn bng. + Dao ng tun hon l dao ng m sau nhng khong thi gian bng nhau vt tr li v tr v chiu chuyn ng nh c (tr li trng thi ban u). * Dao ng iu ha + Dao ng iu ha l dao ng trong li ca vt l mt hm csin (hoc sin) ca thi gian. + Phng trnh dao ng: x = Acos(t + )Trong : x (m;cm hoc rad): Li (to ) ca vt; cho bit lch v chiu lch ca vt so vi VTCB. A>0(m;cmhocrad):Lbin(liccicavt);chobitlchcci ca vt so vi VTCB. (t + ) (rad): L pha ca dao ng ti thi im t; cho bit trng thi dao ng (v tr v chiu chuyn ng) ca vt thi im t. (rad): L pha ban u ca dao ng; cho bit trng thi ban u ca vt. (rad/s): L tn s gc ca dao ng iu ho; cho bit tc bin thin gc pha + im P dao ng iu ha trn mt on thng lun lun c th dc coi l hnh chiu ca mt im M chuyn ng trn u trn ng knh l on thng . * Chu k, tn sca dao ng iu ho + Chu k T(s): L khong thi gian thc hin mt dao ng ton phn. Chnh l khong thi gian ngn nht vt tr li v tr v chiu chuyn ng nh c (tr li trng thi ban u). + Tn s f(Hz):L s dao ng ton phn thc hin c trong mt giy. + Lin h gia , T v f: = T 2 = 2f.I CNG V DAO NG IU HO - S 1 1 -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN29 * Vn tc v gia tc ca vt dao ng iu ho + Vn tc l o hm bc nht ca li theo thi gian: v = x' = - Asin(t + ) = Acos(t + + 2)Vn tc ca vt dao ng iu ha bin thin iu ha cng tn s nhng sm pha hn 2 so vi vi li .- v tr bin (x = A): ln 'v'min = 0 - v tr cn bng (x = 0): ln 'v'min =A. Gi tr i s: vmax = A khi v>0 (vt chuyn ng theo chiu dng qua v tr cn bng) vmin = -A khi v 0 '2. .10. (2 )2v x cos t = = +> 0. tho mn iu kin ny ta chn2. . .22 6t k + = + 16t k= + vi k = 1, 2, 3, 4,... (v t > 0) Vt i qua v tr x = 5cm ln hai theo chiu dngk = 2. Vy ta c t = 1 1126 6 + = (s). VD3.Mtvtdaongiuhoviphngtrnh:10.sin( . )2x t = (cm).Xcnhthi im vt i qua v tr c li x = -5 2 (cm) ln th ba theo chiu m. Li Gii Thi im vt i qua v tr c li x = -5 2 (cm) theo chiu m c xc nh theo phng trnh sau : 210.sin( . ) 5 2 sin( ) sin( )2 2 2 4x t t = = = = . Suy ra.22 4.22 4t kt k = + = + + ( k Z ) . Ta c vn tc ca vt l : '.10. ( )2v x cos t = = V vt i qua v tr c li x = -5 2 (cm) theo chiu m nn v < 0. Vy ta c: '.10. ( )2v x cos t = = < 0. tho mn iu kin ny ta chn .22 4t k = + + 72.4t k = + ( 0,1, 2, 3,... k = ; t > 0 ) Vt i qua v tr c li x = -5 2 (cm) theo chiu m, ln 3 l : 7 232.24 4t = + = (s). VD4. Mt vt dao ng iu ho vi phng trnh :10.sin(10. . )2x t = +(cm). Xc nh thi im vt i qua v tr c li x = 5cm ln th 2008. Li Gii Thi im vt i qua v tr c li x = 5cm c xc nh t phng trnh:

110.sin(10. . ) 5 sin(10. . )2 2 2x t t = + = + = 10. . .22 6510. . .22 6t kt k + = ++ = + v t > 0 nn ta c 130 5kt = + vi k = 1, 2, 3, 4,... (1)Hoc 130 5kt = +vi k = 0, 1, 2, 3, 4,... (2) + (1) ng vi cc thi im vt i qua v tr x = 5cm theo chiu dng ( v > 0 ). -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN47

'100 . (10 )2v x cos t = = +> 0v t > 0 + (2) ng vi cc thi im vt i qua v tr x = 5cm theo chiu m ( v < 0 ).

'100 . (10 )2v x cos t = = +< 0v t > 0 + Khi t = 010.sin 102x cm= = , vt bt u dao ng t v tr bin dng. Vt i qua v tr x = 5cm ln th nht theo chiu m, qua v tr ny ln 2 theo chiu dng. Ta c ngay vt qua v tr x = 5cm ln th 2008 theo chiu dng, trong s 2008 ln vt qua v tr x = 5cm th c 1004 ln vt qua v tr theo chiu dng. Vy thi im vt qua v tr x = 5cm ln th 2008 l :130 5kt = +vi k = 1004.

1 1004 6024 1 602330 5 30 30t= + = = (s). VD5.Mt vt dao ng iu ho c bin bng 4 (cm) v chu k bng 0,1 (s).Vit phng trnh dao ng ca vt khi chn t = 0 l lc vt i qua v tr cn bng theo chiu dng. Tnh khong thi gian ngn nht vt i t v tr c li x1 = 2 (cm) n v tr x2 = 4 (cm). Li Gii a) Phng trnh dao ng : Phng trnh c dng : .sin( . ) x A t = +Trong : A = 4cm, 2 220 ( / )0,1rad sT = = = . Chn t = 0 l lc vt qua VTCB theo chiu dng, ta c : x0 = A.sin= 0, v0 = A. .cos> 00( ) rad = .Vy4.sin(20 . ) x t = (cm)b) Khong thi gian ngn nht vt i t v tr c li x1 = 2 (cm) n v trx2 = 4 (cm). + Cch 1:- 114sin(20 . ) 2 sin(20 . )2x x t t = = = 11( )120t s = ( v v > 0 ) - 24sin(20 . ) 4 sin(20 . ) 1 x x t t = = =21( )40t s = ( v v > 0 ) Kt lun : Khong thi gian ngn nht vt i t v tr c li x1 = 2 (cm) n v tr x2 = 4 (cm) l : t = t2 t1 = 1 1 1( )40 120 60s = . + Cch 2: Chn t = 0 l lc vt i qua v tr c li x0 = x1 = 2cm theo chiu dng, ta c : 0 114.sin( ) 2 sin2 6x x x = = = = = = (rad) ( v v > 0 ) 4.sin(20 . )6x t = + (cm). Thigianvtitvtrx0nvtrx=4cmcxcnhbiphngtrnh:14.sin(20 . ) 4 sin(20. . ) 1 ( )6 6 60x t t t s = + = + = = *Dng bi tp: Xc nh thi im vt i qua ly x0, c gi tr vn tc v0 PHNG PHP Phng trnh dao ng c dng:x = Acos(t + ) cm O 2 4 x(cm) -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN48 Phng trnh vn tc: v = -Asin(t + ) cm/s 1) Khi vt i qua ly x0 th x0= Acos(t + ) cos(t + ) = 0xA=cosb 2 t b k + = +2 b kt = + s vi kN khib >0 v kN* khib >v kN* khi 00dd < 0 * V D MINH HA: VD 1: Mt vt dao ng iu ho vi phng trnh x = 8cos(2t) cm. Thi im th nht vt i qua v tr cn bng l: A) 14s B) 12s C) 16s D) 13sHD Gii: Chn A Cch 1: Vt qua VTCB: x = 0 2t = /2 + k 1k 4 2kt N = + Thi im th nht ng vi k = 0 t = 1/4 (s) Cch 2: S dng mi lin h gia dh v chuyn ng trn u. Vt i qua VTCB, ng vi vt chuyn ng trn u qua M1 v M2. V = 0, vt xut pht t M0 nn thi im th nht vt qua VTCB ng vi vt qua M1.Khi bn knh qut 1 gc = /2 14t s= =VD 2:Mt vt dao ng iu ho vi phng trnh x = 4cos(4t + 6) cm. Thi im th 3 vt qua v tr x = 2cm theo chiu dng. A) 9/8 sB) 11/8 sC) 5/8 sD) 1,5 s HD Gii: Chn B Cch 1: Ta c 4 os(4 ) 2264 20 6 316 sin(4 ) 06x c txt kvv t = + == + = + > = + >

*1k N8 2kt = + Thi im th 3 ng vi k = 3 118t s =O x M1 M2 A -A M0 O x M1 MA -M0 -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN49 Cch 2: S dng mi lin h gia dao ng iu ho v chuyn ng trn u. Vt qua x = 2 theo chiu dng l qua M2. Qua M2 ln th 3 ng vi vt quay c 2 vng (qua 2 ln) v ln cui cng i t M0 n M2. Gc qut = 2.2 +32 118t s= =VD 3:Mt vt dao ng iu ho vi phng trnh x = 4cos(4t + 6) cm. Thi im th 2009 vt qua v tr x=2cm. A) 1204924s B) 1206124s C) 1202524s D) p n khc HD Gii:Chn A Cch 1:*14 2k N6 3 24 221 k N 4 28 2 6 3kt k txkt t k + = + = + = = + + = + Vtqualnth2009(l)ngvinghimtrn 2009 110042k= = 1 12049502 = s24 24t = +Cch 2: Vt qua x =2 l qua M1 v M2.Vt quay 1 vng (1 chu k) qua x = 2 l 2 ln. Qua ln th 2009 th phi quay 1004 vng ri i t M0 n M1. Gc qut 1 120491004.2 5026 24 24t s = + = = + = *DNG BI TP: XC NH S LN VT QUA LI X, QUNG NG I C TRONG KHONG THI GIAN CHO Phng php Phng trnh dao ng c dng:x = Acos(t + ) cm Phng trnh vn tc: v = -Asin(t + ) cm/s Tnh s chu k dao ng t thi im t1 n t2 : 2 1t t mN nT T= = + , vi 2T=Trong mt chu k : + vt i c qung ng 4A+ Vt i qua ly bt k 2 ln * Nu m= 0 th:+ Qung ng i c: ST = 4nA + S ln vt i qua x0 lMT= 2n * Nu m0 th: + Khi t=t1 ta tnh x1 = Acos(t1 + )cm v v1 dng hay m (khng tnh v1) + Khi t=t2 ta tnh x2 = Acos(t2 + )cm v v2 dng hay m (khng tnh v2) Sau v hnh ca vt trong phn l mT chu k ri da vo hnh v tnh Sl v s ln Ml vt i qua x0 tng ng. Khi :+ Qung ng vt i c l: S=ST +Sl

+ S ln vt i qua x0 l:M=MT+ Ml O xM1 MA -M0 -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN50 * V d: 1 0 21 20, 0x x xv v> > > > ta c hnh v:Khi + S ln vt i qua x0 lMl= 2n + Qung ng i c:Sl = 2A+(A-x1)+(A-2x ) =4A-x1-2x V d 1: Mt vt dao ng iu ha theo phng trnh x = 4 cos(2t + /3). Tnh qung ng m vt i c trong thi gian 3,75s. Gii. D dng nhn thy, trong thi gian 1 chu k T vt dao ng i c qung ng 4A Chu k dao ng ca vt: T = 1s(bn c t tnh) Khong thi gian 3,75s = 3 chu k T + 0,75s + Qung ng vt i c trong 3s = qung ng vt i trong 3 chu k = 3 4A = 48 + Qung ng vt i c trong 0,75s c xc nh theo hnh v di y: S0,75s = AO + OB + BO + OC = AO + 4 + 4 + OC = 10 + 2 3 cm trong OA = 4. sin 300 = 2 cm v OC = 4 . sin 600 = 2 3cm Vytng qung ng m vt i c: S = 58 + 2 3cm = 61,6 cm III. TRC NGHIM TNG HP: Cu 1: Mt vt dao ng iu ho vi tn s gc = 5rad/s. Lc t = 0, vt i qua v tr c li x=-2cmvcvntc10(cm/s)hngvphavtrbingnnht.Phngtrnhdao ng ca vt l A. x = 2 2 cos(5t + 4)(cm).B. x = 2cos (5t - 4)(cm). C. x =2 cos(5t + 45)(cm).D. x = 2 2 cos(5t + 43)(cm). -A A Ox2 x1 x0 X -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN51 Cu 2:Mt vt dao ng iu ho trn qu o di 10cm vi tn s f = 2Hz. thi im banut= 0,vtchuynngngcchiudng.thiimt=2s,vtc giatca = 4 3 m/s2. Ly 2 10. Phng trnh dao ng ca vt l A. x = 10cos(4t +/3)(cm).B. x = 5cos(4t - /3)(cm). C. x = 2,5cos(4t +2/3)(cm).D. x = 5cos(4t +5/6)(cm). Cu 3: Mt vt dao ng iu ho khi i qua v tr cn bng theo chiu dng thi im ban u. Khi vt c li 3cm th vn tc ca vt bng 8cm/s v khi vt c li bng 4cm th vn tc ca vt bng 6cm/s. Phng trnh dao ng ca vt c dng A. x = 5cos(2t- 2 / )(cm).B. x = 5cos(2t+) (cm). C. x = 10cos(2t- 2 / )(cm).D. x = 5cos( t+ 2 / )(cm). Cu 4: Mt vt c khi lng m = 1kg dao ng iu ho vi chu k T = 2s. Vt qua v tr cn bng vi vn tc 31,4cm/s. Khi t = 0 vt qua li x = 5cm theo chiu m qu o. Ly 2 10. Phng trnh dao ng iu ho ca con lc l A. x = 10cos( t +/3)(cm).B. x = 10cos( 2 t +/3)(cm). C. x = 10cos( t - /6)(cm).D. x = 5cos( t - 5/6)(cm). Cu 5: Mt vt dao ng iu ho trong mt chu k dao ng vt i c 40cm v thc hin c 120 dao ng trong 1 pht. Khi t = 0, vt i qua v tr c li 5cm v ang theo chiu hng v v tr cn bng. Phng trnh dao ng ca vt c dng l A.) cm )(3t 2 cos( 10 x+ = .B.) cm )(3t 4 cos( 10 x+ = . C.) cm )(3t 4 cos( 20 x+ = .D.) cm )(32t 4 cos( 10 x+ = . Cu 6: Mt vt dao ng iu ho c chu k T = 1s. Lc t = 2,5s, vt nng i qua v tr c li l x =2 5 cm vi vn tc l v =2 10 cm/s. Phng trnh dao ng ca vt l A.). cm )(4t 2 cos( 10 x+ = B.). cm )(4t cos( 10 x =C.). cm )(4t 2 cos( 20 x = D.). cm )(4t 2 cos( 10 x =Cu 7: Mt vt dao ng iu ho i qua v tr cn bng theo chiu m thi im ban u. Khi vt i qua v tr c li x1 = 3cm th c vn tcv1 = 8 cm/s, khi vt qua v tr c li x2 = 4cm th c vn tc v2 = 6 cm/s. Vt dao ng vi phng trnh c dng: A.). cm )( 2 / t 2 cos( 5 x + = B.). cm )( t 2 cos( 5 x + =C.). cm )( 2 / t 2 cos( 10 x + = D.). cm )( 2 / t 4 cos( 5 x =Cu 8: Mt vt dao ng c h thc gia vn tc v li l116x640v2 2= + (x:cm; v:cm/s). Bit rng lc t = 0 vt i qua v tr x = A/2 theo chiu hng v v tr cn bng. Phng trnh dao ng ca vt l A.). cm )( 3 / t 2 cos( 8 x + = B.). cm )( 3 / t 4 cos( 4 x + =C.). cm )( 3 / t 2 cos( 4 x + = D.). cm )( 3 / t 2 cos( 4 x =Cu9: Mt vt dao ng iu ho theo phng trnh x = 10cos( t 10 )(cm). Thi im vt i qua v tr N c li xN = 5cm ln th 2009 theo chiu dng l A. 4018s.B. 408,1s.C. 410,8s.D. 401,77s. Cu10: Mt vt dao ng iu ho theo phng trnh x = 10cos( t 10 )(cm). Thi im vt i qua v tr N c li xN = 5cm ln th 1000 theo chiu m l A. 199,833s.B. 19,98s.C. 189,98s.D. 1000s. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN52 Cu11: Mt vt dao ng iu ho theo phng trnh x = 10cos( t 10 )(cm). Thi im vt i qua v tr N c li xN = 5cm ln th 2008 l A. 20,08s.B. 200,77s.C. 100,38s.D. 2007,7s. Cu12:Vtdao ngiu hotheo phngtrnhx =cos( t-2/3)(dm).Thigian vti c qung ng S = 5cm k t thi im ban u t = 0 l A. 1/4s.B. 1/2s.C. 1/6s.D. 1/12s. Cu13:Vt dao ng iu ho theo phng trnh x = 5cos(10t+)(cm). Thi gian vt i c qung ng S = 12,5cm k t thi im ban u t = 0 l A. 1/15s.B. 2/15s.C. 1/30s.D. 1/12s. Cu14:MtchtimdaongdctheotrcOx.Theophngtrnhdaongx= 2cos(2t+)(cm). Thi gian ngn nht vt i t lc bt u dao ng n lc vt c li x = 3 cm l A. 2,4s.B. 1,2s.C. 5/6s.D. 5/12s. Cu15:Mtchtimdaongviphngtrnhdaonglx=5cos(8t-2/3)(cm). Thi gian ngn nht vt i t lc bt u dao ng n lc vt c li x = 2,5cm l A. 3/8s.B. 1/24s.C. 8/3s.D. 1/12s. Cu16:MtchtimdaongdctheotrcOx.Phngtrnhdaonglx= 4cos(5t)(cm). Thi gian ngn nht vt i t lc bt u dao ng n lc vt i c qung ng S = 6cm l A. 3/20s.B. 2/15s.C. 0,2s.D. 0,3s. Cu17: Mt vt dao ng iu ho c chu k T = 4s v bin dao ng A = 4cm. Thi gian vt i t im c li cc i v im c li bng mt na bin l A. 2s. B. 2/3s.C. 1s. D. 1/3s. Cu18: Mt vt dao ng iu ho vi tn s bng 5Hz. Thi gian ngn nht vt i t v tr c li bng - 0,5A(A l bin dao ng) n v tr c li bng +0,5A l A. 1/10s.B. 1/20s.C. 1/30s.D. 1/15s. Cu19:Mtvtdaongiuhoviphngtrnhx=Acos( + t ).Bittrongkhong thi gian 1/30s u tin, vt i t v tr x0 = 0 n v tr x = A 3 /2 theo chiu dng. Chu k dao ng ca vt l A. 0,2s.B. 5s. C. 0,5s.D. 0,1s. Cu20:Mtvtdaongiuhotheophngtrnh) cm )( 2 / t 20 cos( 4 x = .Thigian ngn nht vt i t v tr c li x1 = 2cm n li x2 = 4cm bng A. 1/80s.B. 1/60s.C. 1/120s.D. 1/40s. Cu21: Mt vt dao ng iu ho theo phng trnh x = 4cos20t(cm). Qung ng vt i c trong thi gian t = 0,05s l A. 8cm.B. 16cm.C. 4cm.D. 12cm. Cu22: Mt vt dao ng iu ho theo phng trnh x = 5cos(2t- ) 2 / (cm). K t lc t = 0, qung ng vt i c sau 5s bng A. 100m.B. 50cm.C. 80cm.D. 100cm. Cu23: Mt vt dao ng iu ho theo phng trnh x = 5cos(2t- ) 2 / (cm). K t lc t = 0, qung ng vt i c sau 12,375s bng A. 235cm.B. 246,46cm.C. 245,46cm.D. 247,5cm. Cu24: Mt vt dao ng iu ho theo phng trnh x = 2cos(4t - /3)(cm). Qung ng vt i c trong thi gian t = 0,125s l A. 1cm.B. 2cm.C. 4cm.D. 1,27cm. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN53 Cu25: Mt cht im dao ng dc theo trc Ox. Phng trnh dao ng l x = 8cos(2t +)(cm). Sau thi gian t = 0,5s k t khi bt u chuyn ng qung ng S vt i c l A. 8cm.B. 12cm.C. 16cm.D. 20cm. Cu26: Mt cht im dao ng dc theo trc Ox. Phng trnh dao ng l x = 3cos(10t -/3)(cm). Sau thi gian t = 0,157s k t khi bt u chuyn ng, qung ng S vt i lA. 1,5cm.B. 4,5cm.C. 4,1cm.D. 1,9cm. Cu27:Chomtvtdaongiuhoviphngtrnhx=10cos(2t-5/6)(cm).Tm qung ng vt i c k t lc t = 0 n lc t = 2,5s. A. 10cm.B. 100cm.C. 100m.D. 50cm. Cu28: Mt vt dao ng iu ho theo phng trnh x = 5cos(32t 2 )(cm). Qung ng vt i c sau thi gian 2,4s k t thi im ban u bng A. 40cm.B. 45cm.C. 49,7cm.D. 47,9cm. Cu29: Mt vt dao ng iu ho c phng trnh x = 5cos( ) 2 / t 2 (cm). Qung ng m vt i c sau thi gian 12,125s k t thi im ban u bng A. 240cm.B. 245,34cm.C. 243,54cm.D. 234,54cm. Cu30:MtchtimdaongdctheotrcOx.Phngtrnhdaonglx= 4cos4t(cm). Vn tc trung bnh ca cht im trong 1/2 chu k l A. 32cm/s.B. 8cm/s.C. 16cm/s. D. 64cm/s. Cu31: Mt vt dao ng iu ho vi tn s f = 2Hz. Tc trung bnh ca vt trong thi gian na chu k l A. 2A.B. 4A.C. 8A.D. 10A. Cu32: Mt vt dao ng iu ho theo phng trnh) cm )( 3 / 2 t 8 cos( 4 x = . Tc trung bnh ca vt khi i t v tr c li x1 =3 2 cm theo chiu dng n v tr c li x2 = 3 2 cm theo chiu dng bng A.3 8 , 4 cm/s.B.3 48 m/s. C.2 48 cm/s.D.3 48 cm/s. Cu33: Mt vt dao ng iu ho theo phng trnh x = 5cos(6t 2 )(cm).Tc trung bnh ca vt trong mt chu k dao ng bng A. 20m/s.B. 20cm/s.C. 5cm/s.D. 10cm/s. Cu34:Mt vt dao ng iu ho vi phng trnh x = 10cos( 8 / t 4 + )(cm). Bit thi im t c li l 4cm. Li dao ng thi im sau 0,25s l A. 4cm.B. 2cm.C. -2cm.D. - 4cm. Cu35:Mtvtdaongiuhoviphngtrnhx=10cos(8t 4+ )(cm).Bitthi im t c li l -8cm. Li dao ng thi im sau 13s l A. -8cm.B. 4cm.C. -4cm.D. 8cm. Cu36:Mtvtdaongiuhoviphngtrnhx=5cos( 3 / t 5 + )(cm).Bitthi im t c li l 3cm. Li dao ng thi im sau 1/10(s) l A. 4cm.B. 3cm.C. -3cm.D. 2cm. Cu37:Mtvtdaongiuhoviphngtrnhx=5cos( 3 / t 5 + )(cm).Bitthi im t c li l 3cm. Li dao ng thi im sau 1/30(s) l A. 4,6cm.B. 0,6cm.C. -3cm.D. 4,6cm hoc 0,6cm. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN54 Cu38: Mt vt dao ng theo phng trnh x = 3cos(5t - 2/3) +1(cm). Trong giy u tin vt i qua v tr N c x = 1cm my ln ? A. 2 ln.B. 3 ln.C. 4 ln.D. 5 ln. Cu39: Mt vt dao ng iu ho vi chu k T =10 / (s) v i c qung ng 40cm trong mt chu k dao ng. Tc ca vt khi i qua v tr c li x = 8cm bng A. 1,2cm/s.B. 1,2m/s.C. 120m/s.D. -1,2m/s. Cu40: Mt vt dao ng iu ho vi chu k T =10 / (s) v i c qung ng 40cm trong mt chu k dao ng. Gia tc ca vt khi i qua v tr c li x = 8cm bng A. 32cm/s2.B. 32m/s2.C. -32m/s2.D. -32cm/s2. Cu41: Mt vt dao ng iu ho trn mt on thng di 10cm v thc hin c 50 dao ng trong thi gian 78,5 giy. Vn tc ca vt khi qua v tr c li x = -3cm theo chiu hng v v tr cn bng l A. 16m/s.B. 0,16cm/s. C. 160cm/s.D. 16cm/s. Cu42: Mt vt dao ng iu ho trn mt on thng di 10cm v thc hin c 50 dao ng trong thi gian 78,5 giy. Gia tc ca vt khi qua v tr c li x = -3cm theo chiu hng v v tr cn bng l A. 48m/s2.B. 0,48cm/s2.C. 0,48m/s2. D. 16cm/s2. Cu43: Mt vt dao ng iu ho vi chu k T = 0,4s v trong khong thi gian vt i c qung ng 16cm. Tc trung bnh ca vt khi i t v tr c li x1 = -2cm n v tr c li x2 =3 2 cm theo chiu dng l A. 40cm/s.B. 54,64cm/s.C. 117,13cm/s.D. 0,4m/s. Cu44:Mtvtdaongiuhoviphngtrnht 5 cos 4 x = (cm).Thiimutin vt c vn tc bng na ln vn tc cc i l A.. s301B.. s61C.. s307D.. s3011 Cu45:Mtvtckhilngm=200gdaongdctheotrcOxdotcdngcalc phc hi F = -20x(N). Khi vt n v tr c li + 4cm th tc ca vt l 0,8m/s v hng ngc chiu dng l thi im ban u. Ly g = 2 . Phng trnh dao ng ca vt c dng A.). cm )( 11 , 1 t 10 cos( 2 4 x + =B.). cm )( 11 , 1 t 10 cos( 5 4 x + =C.). cm )( 68 , 2 t 10 cos( 5 4 x + = D.). cm )( 11 , 1 t 10 cos( 5 4 x + =Cu46: Mt con lc gm mt l xo c cng k = 100N/m, khi lng khng ng k v mt vt nh khi lng 250g, dao ng iu ho vi bin bng 10cm. Ly gc thi gian t = 0 l lc vt i qua v tr cn bng. Qung ng vt i c trong t =/24s u tin l A. 5cm.B. 7,5cm.C. 15cm.D. 20cm. Cu47: Mt vt dao ng iu ho khi i qua v tr cn bng c tc bng 6m/s v gia tc khi vt v tr bin bng 18m/s2. Tn s dao ng ca vt bng A. 2,86 Hz.B. 1,43 Hz.C. 0,95 Hz.D. 0,48 Hz. Cu48:HaichtimMvNcngxutphttgcvbtudaongiuhocng chiu dc theo trc x vi cng bin nhng vi chu k ln lt l 3s v 6s. T s ln vn tc khi chng gp nhau l A. 1:2.B. 2:1.C. 2:3.D. 3:2. Cu49: Mt vt dao ng iu ho theo phng trnh) cm )( 3 / t cos( 10 x + = . Thi gian tnh t lc vt bt u dao ng ng(t = 0) n khi vt i c qung ng 30cm l A. 1,5s.B. 2,4s.C. 4/3s.D. 2/3s. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN55 Cu50:Phngtrnhx=Acos( 3 / t )biudindaongiuhocamtchtim. Gc thi gian c chn khi A. li x = A/2 v cht im ang chuyn ng hng v v tr cn bng. B. li x = A/2 v cht im ang chuyn ng hng ra xa v tr cn bng. C. li x = -A/2 v cht im ang chuyn ng hng v v tr cn bng. D. li x = -A/2 v cht im ang chuyn ng hng ra xa v tr cn bng. Cu 51(2011): Mt cht im dao ng iu ha trn trc Ox vi bin 10 cm, chu k 2 s. Mc th nng v tr cn bng. Tc trung bnh ca cht im trong khong thi gian ngn nht khi cht im i t v tr c ng nng bng 3 ln th nng n v tr c ng nng bng 13 ln th nng l A. 26,12 cm/s.B. 7,32 cm/s.C. 14,64 cm/s.D. 21,96 cm/s. Khng c ti sn no qu bng tr thng minh, khng c vinh quang no ln hn hc vn v hiu bit P N S 2 1 D2D3A4A5B6A7A8C9D10A 11 B12C13B14D15B16B17B18C19A20B 21 A22D23B24D25C26D27B28D29C30A 31C32D33B34D35A36A37D38D39B40C 41D42 C43B44A45B46C47D48B49C50B 51D52 5354555657585960 Hvtnhcsinh :..Trng:THPT. *DNG BI TP: IU KIN HAI VT DAO NG CNGDAO NG Phng php - Trng hp 1.Khi m0 th ln m v kch thch cho h dao ng theo phng song song vi b mt tip xc gia hai vt. m0 khng b trt trn m th lc ngh ma st cc i m mtcdngm0trongqutrnh dao ng phi nh hn hoc bnglcmast trt gia hai vt. fmsn (Max) < fmst 20 0 0 0. . . . . . . m a m g m x m g u u 20 0. . . . m A m g u Trong :ul h s ma sttrt. -Trng hp 2.Khi m0 t ln m v kch thch cho h dao ng theo phng thng ng. m0 khng ri khi m trong qu trnh dao ng th: amax 2. g A g VDMINHHA.Chochdaongnhhnhv,khilng caccvttngnglm=1kg,m0=250g,lxockhilng khngngk,cngk=50(N/m).Mastgiamvmtphng I CNG V DAO NG IU HO - S 3 3 mmk -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN56 nm ngang khng ng k. H s ma st gia m v m0 l0, 2 u = . Tm bin dao ng lnnhtca vtmm0khngtrt trnbmt ngang ca vt m. Cho g = 10(m/s2), 210 . Li Gii - Khi m0 khng trt trn b mt ca m th h hai vt dao ng nh l mt vt ( m+m0 ). Lc truyn gia tc cho m0 l lc ma st ngh xut hin gia hai vt.

20 0. . .msnf m a m x = = . Gi tr ln nht ca lc ma st ngh l : 20( ) . .msnf Max m A =(1) - Nu m0 trt trn b mt ca m th lc ma st trt xut hin gia hai vt l lc ma st trt : 0. .mstf m g u =(2) - m0 khng b trt trn m th phi c: 20 0( ) . . . .msn mstf Max f m A m g u 2.gAu ; m 20km m =+ nn ta c : 0. . 0, 05 5 .m mA g A m A cmku+ Vy bin ln nht ca m m0 khng trt trn m l Amax = 5cm. Bi2.Mtvtckhilngm=400gcgntrnmtlxothng ng c cng k = 50(N/m). t vt m c khi lng 50g ln trn m nh hnhv.Kchthchchomdaongtheophngthngngvibin nh. B qua sc cn ca khng kh. Tm bin dao ng ln nht ca m m khng ri khi m trong qu trnh dao ng. Ly g = 10 (m/s2). Li Gii m khng ri khi m trong qu trnh dao ng th h ( m+m) dao ng vi cng gia tc. Taphic:amax 2. g A g 2( ').0, 09g m m gA A A mk + 9 9maxA cm A cm = .

* TRC NGHIM TNG HP Cu 1: Chu k ca dao ng iu ha l A. khong thi gian gia hai ln vt i qua v tr cn bng. B.thi gian ngn nht vt c li nh c. C.khong thi gian vt i t li cc i m n li cc dng. D. khong thi gian m vt thc hin mt dao ng. Cu 2:Pha ban u ca dao ng iu ha ph thuc A. cch chn gc ta v gc thi gian. B.nng lng truyn cho vt vt dao ng. C.c tnh ca h dao ng. D. cch kch thch vt dao ng. Cu 3:Vt dao ng iu ha c tc bng 0 khi vt v tr A. m lc tc dng vo vt bng 0.B.cn bng. C.m l xo khng bin dng.D. c li cc i. Cu 4:Vt dao ng iu ha c ng nng bng 3 th nng khi vt c li A. x = 13A.B.x = 22A.C.x = 0,5A.D. x = 32A. m m k -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN57 Cu 5: Nng lng vt dao ng iu ha A. bng vi th nng ca vt khi vt qua v tr cn bng. B.bng vi th nng ca vt khi vt c li cc i. C.t l vi bin dao ng. D. bng vi ng nng ca vt khi c li cc i. Cu 6: Vt dao ng iu ha khi A. hai bin tc bng 0, ln gia tc bng 0. B.qua v tr cn bng tc cc i, gia tc bng 0. C.qua v tr cn bng tc bng 0, ln gia tc cc i. D. qua v tr cn bng tc bng 0, ln gia tc bng 0. Cu 7: Gia tc ca vt dao ng iu ha bng 0 khi A. th nng ca vt cc i.B. vt hai bin. C.vt v tr c tc bng 0.D. hp lc tc dng vo vt bng 0. Cu 8:Vt dao ng iu ha c ng nng bng th nng khi vt c li A. x = A.B.x = 0.C.x = 22A.D. x = 12A. Cu 9:Vtdao ngiu ha vi binA.Thi gianngn nhtvti t vtrcn bng n li x = 0,5.A l 0,1 s. Chu k dao ng ca vt l A. 0,4 s.B.0,8 s.C.0,12 s.D. 1,2 s. Cu 10:Vt dao ng iu ha theo phng trnh : x = 4cos(20t - 2) cm. Qung ng vt i trong 0,05 s l A. 16 cm.B.4 cm.C.8 cm.D. 2 cm. Cu11:Vtdaongiuhatheophngtrnh:x=2cos4tcm.Qungngvti trong 13 s (k t t = 0 ) l A. 4 cm.B.5 cm.C.2 cm.D. 1 cm. Cu 12: Vt dao ng iu ha theo phng trnh : x = 4cos(20 t - 23) cm. Tc vt sau khi i qung ng S = 2 cm (k t t = 0) l A. 20 cm/s.B.60 cm/s.C.80 cm/s.D. 40 cm/s. Cu 13: Vt dao ng iu ha theo phng trnh : x = 5cos(10t - ) cm. Thi gian vt i c qung ng S = 12,5 cm (k t t = 0) l A. 115 s.B. 112 s.C. 215 s.D. 130 s. Cu 14: Gi k l cng l xo; A l bin dao ng; l tn s gc. Biu thc tnh nng lng con lc l xo dao ng iu ha l A. W =12mA. B.W = 12mA2. C.W = 12KA.D. W = 12m2A2. Cu 15: Chu k dao ng con lc l xo tng 2 ln khi A. bin tng 2 ln. B.khi lng vt nng tng gp 4 ln. C.khi lng vt nng tng gp 2 ln.D. cng l xo gim 2 ln. Cu 16: Nng lng dao ng con lc l xo gim 2 ln khi A. khi lng vt nng gim 4 ln.B. cng l xo gim 2 ln. C.bin gim 2 ln.D. khi lng vt nng gim 2 ln. Cu 17: i vi dao ng iu ha, iu g sau y sai ? -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN58 A. Lc ko v c gi tr cc i khi vt qua v tr cn bng. B.Nng lng dao ng ph thuc cch kch thch ban u. C.Thi gian vt i t bin ny sang bin kia l 0,5 T D. Tc t gi tr cc i khi vt qua v tr cn bng. Cu 18: Vt dao ng iu ha khi i t bin dng v v tr cn bng th A. li vt c gi tr dng nn vt chuyn ng nhanh dn. B.li vt gim dn nn gia tc ca vt c gi tr dng. C.vt ang chuyn ng nhanh dn v vn tc ca vt c gi tr dng. D. vt ang chuyn ng ngc chiu dng v vn tc c gi tr m. Cu 19: Khi vt dao ng iu ha, i lng khng thay i l A. th nng.B.tc .C.tn s.D. gia tc. Cu 20: Con lc l xo dao ng iu ha vi tn s 5 Hz, th nng ca con lc s bin thin vi tn s A. f = 10 Hz.B.f = 20 Hz.C.f = 2,5 Hz.D. f = 5 Hz. Cu 21: Vt dao ng iu ha theo phng trnh x = Acos(t + ); chn gc thi gian lc vt c vn tc v = + 12vmax v ang c li dng th pha ban u ca dao ng l: A. = 4 B. = - 6 C. = 6 D. = - 3

Cu 22: Gi x l li , k l h s t l (k > 0). Lc tc dng lm vt dao ng iu ha c dng A. F = -kxB.F = kxC.F = -kx2 D. F = kx2 Cu 23: Con lc l xo dao ng iu ha trn phng ngang, tc vt trit tiu khi A. lc tc dng vo vt bng 0B. ln li cc i. C.l xo c chiu di t nhinD. gia tc vt bng 0. Cu 24: Mt vt chuyn ng theo phng trnh x = - cos(4t - 23 ) (x c n v cm; t c n v giy). Hy tm cu tr li ng. A. Vt ny khng dao ng iu ha v c bin m. B.Ti t = 0: Vt c li x = 0,5 cm v ang i v v tr cn bng. C.Ti t = 0: Vt c li x = 0,5 cm v ang i ra xa v tr cn bng. D. Vt ny dao ng iu ha vi bin 1 cm v tn s bng 4 . Cu 25: Mt vt dao ng iu ho vi bin 4cm, c sau mt khong thi gian 1/4 giy thngnnglibngthnng.Qungnglnnhtmvtictrongkhongthi gian 1/6 giy l A. 8 cm.B. 6 cm.C. 2 cm.D. 4 cm. Cu 26: Pht biu no sau y v ng nng v th nng trong dao ng iu ho l khng ng? A. Th nng t gi tr cc tiu khi gia tc ca vt t gi tr cc tiu. B. ng nng t gi tr cc i khivt chuyn ng qua v tr cn bng. C. Th nng t gi tr cc i khi tc ca vt t gi tr cc i. D. ng nng t gi tr cc tiu khi vt mt trong hai v tr bin. Cu 27: Trong dao ng iu ho, gia tc bin i A. tr pha/ 2 so vi li . B. cng pha vi so vi li . C. ngc pha vi vn tc. D. sm pha/ 2 so vi vn tc. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN59 Cu 28: Ti mt thi im khi vt thc hin dao ng iu ho vi vn tc bng 1/2 vn tc cc i , vt xut hin ti li bng bao nhiu ? A.A3. B.A2. C. A 2 .D.A 23. Cu29:Mtconlclxo,khilngcavtbng2kgdaongtheophngtrnh os( t+ ) x Ac = . C nng dao ng E = 0,125 (J). Ti thi im ban u vt c vn tc v0 = 0,25 m/s v gia tc 26, 25 3( / ) = a m s . cng ca l xo l A. 425(N/m). B. 3750(N/m).C. 150(N/m).D. 100 (N/m). Cu 30: Mt con lc c chu k 0,1s bin dao ng l 4cm khong thi gian ngn nht n dao ng t li x1 = 2cm n li x2 = 4cm l A. 601s. B. 1201s.C. 1s30 .D. 401s. Cu 31: Chn cu sai: Trong dao ng iu ho, khi lc phc hi c ln cc i th A. vt i chiu chuyn ng.B. vt qua v tr cn bng. C. vt qua v tr bin. D. vt c vn tc bng 0. Cu 32: Nu vo thi im ban u, vt dao ng iu ha i qua v tr cn bng th vo thi im T/12, t s gia ng nng v th nng ca dao ng l A. 1.B. 3.C. 2. D. 1/3. Cu 33: Khi con lc dao ng vi phng trnh) ( 10 cos 5 mm t s =th th nng ca n bin i vi tn s : A. 2,5 Hz.B. 5 Hz.C. 10 Hz. D. 18 Hz. Cu 34: Mt vt dao ng iu ho theo phng trnh x = 4cos(6t +6)cm. Vn tc ca vt t gi tr 12cm/s khi vt i qua ly A.-2 3cm.B. 2cm. C. 2 3cm. D.+2 3cm. Cu 35: Mt vt dao ng iu ha trn trc Ox, xung quanh v tr cn bng l gc ta . Giatccavtphthucvolixtheophngtrnh:a=-4002x.sdaongton phn vt thc hin c trong mi giy l A. 20. B. 10.C. 40.D. 5. Cu 36: Vt dao ng iu ho c gia tc bin i theo phng trnh: ) / )(310 cos( 52s m t a+ = . thi im ban u ( t = 0 s) vt ly A. 5 cm .B. 2,5 cm . C. -5 cm .D. -2,5 cm . Cu 37: Mt cht im dao ng iu ho c vn tc bng khng ti hai thi im lin tip l t1 = 2,2 (s) v t2 = 2,9 (s). Tnh t thi im ban u ( to = 0 s) n thi im t2 cht im i qua v tr cn bng A. 6 ln .B. 5 ln .C. 4 ln . D. 3 ln . Cu38:Vtdaongiuhotheohmcosinvibin4cmvchuk0,5s(ly 210 = ) .Ti mt thi im m pha dao ng bng 37 th vt ang chuyn ng li gn v tr cn bng .Gia tc ca vt ti thi im l A. 320 cm/s2 .B. 160 cm/s2 .C. 3,2 m/s2.D. - 160 cm/s2 . -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN60 Cu 39: Mt con lc l xo dao ng iu ha vi bin 6cm v chu k 1s. Ti t = 0, vt i qua v tr cn bng theo chiu m ca trc to . Tng qung ng i c ca vt trong khong thi gian 2,375s k t thi im c chn lm gc l: A. 48cm. B. 50cm. C. 55,76cm.D. 42cm. Cu 40: Mt vt dao ng iu ha vi tn s bng 5Hz. Thi gian ngn nht vt i t v tr c li x1 = - 0,5A (A l bin dao ng) n v tr c li x2 = + 0,5A l A. 1/10 s.B. 1 s.C. 1/20 s.D. 1/30 s. Cu 41: Mt vt dao ng iu ha vi chu k T = 3,14s. Xc nh pha dao ng ca vt khi n qua v tr x = 2cm vi vn tc v = - 0,04m/s. A. 0. B. 4 rad . C. 6 rad. D. 3 rad. Cu 43: Gia tc tc thi trong dao ng iu hobin i: A. cng pha vi li . B. lch pha 4 vi li C. lch pha vung gc vi li . D. ngc pha vi li . Cu44:Mtvtdaongiuhatheophngtrnhx=5cos(2t)cm.Nutimtthi imnovtangclix=3cmvangchuynngtheochiudngthsau 0,25 s vt c li l A. - 4cm.B. 4cm. C. -3cm.D. 0. Cu45:Mtchtimdaongiuhotheophngtrnh: cm t x )2cos( 3 + = ,phadao ng ca cht im ti thi im t = 1s l A. 0(cm).B. 1,5(s). C. 1,5 (rad).D. 0,5(Hz). Mi khi i mt vi th thch, hy tm mt li i ch khng phi l mt li thot P N S 3 1 D2A3D4C5B6B7D8C9D10C 11B12C13C14D15B16B17A18D19C20A 21B22A23B24B25D26C27D28D29B30A 31B32B33C34C35B36D37C38A39C40D 41B42D43D44B45C Hvtnhcsinh :..Trng:THPT I. TRC NGHIM TNG HP. TNG HP V DAO NG IU HO 4 -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN61 Cu 1: Pht biu no sau y v ng nng v th nng trong dao ng iu ha l khng ng ? A. ng nng v th nng bin i iu ha cng chu k. B. ng nng bin i iu ha cng chu k vi vn tc. C. Th nng bin i iu ha vi tn s gp 2 ln tn s ca li . D. Tng ng nng v th nng khng ph thuc vo thi gian. Cu 2: Pht biu no sau y v ng nng v th nng trong dao ng iu ha l khng ng ? A. ng nng t gi tr cc i khi vt chuyn ng qua v tr cn bng. B. ng nng t gi tr cc tiu khi vt mt trong v tr bin. C. Th nng t gi tr cc i khi vt chuyn ng qua v tr cn bng. D. Th nng t gi tr cc tiu khi gia tc ca vt t gi tr cc tiu. Cu 3: Pht biu no sau y v s so snh li v gia tc l ng ? Trong dao ng iu ha, li , vn tc v gia tc l ba i lng bin i iu ha theo thi gian v c : A. cng bin .B. cng pha.C. cng tn s gc.D. cng pha ban u. Cu 4:Pht biu no sau y v mi quan h gia li , vn tc, gia tc l ng?A. Trong dao ng iu ha vn tc v li lun cng chiu. B. Trong dao ng iu ha vn tc v gia tc lun ngc chiu. C. Trong dao ng iu ha gia tc v li lun ngc chiu. D. Trong dao ng iu ha gia tc v li lun cng chiu. Cu 5: Mt vt dao ng iu ho, c sau mt khong thi gian 2,5s th ng nng li bng th nng. Tn s dao ng ca vt l A. 0,1 Hz.B. 0,05 Hz.C. 5 Hz. D. 2 Hz. Cu 6: Mt vt dao ng iu ho, thi im th hai vt c ng nng bng ba ln th nng k t lc vt c li cc i l 215s . Chu k dao ng ca vt l A. 0,8 s.B. 0,2 s. C. 0,4 s.D. p n khc.Cu 7: Mt vt dao ng iu ho, khi vt c li x1=4cm th vn tc 140 3 / v cm s = ; khi vt c li 24 2 x cm =th vn tc 240 2 / v cm s = . ng nng v th nng bin thin vi chu k A. 0,1 s.B. 0,8 s. C. 0,2 s.D. 0,4 s. Cu 8: Mt con lc l xo nm ngang dao ng iu ho xung quanh v tr cn bng vi chu k T = 10s. t trc ta Ox nm ngang, gc O ti v tr cn bng. Cho rng lc t = 0, vt vtrclix=-1cmvctruynvntc20 3 cm/stheochiudng.Khi phng trnh dao ng ca vt c dng: A. x = 2 sin ( 20t - /6) cm. B.x = 2 sin ( 20t - /3) cm . C. x = 2 cos ( 20t - /6) cm.D.x = 2 sin ( 20t + /6) cm.Cu 9: Nng lng ca mt vt dao ng iu ho l E. Khi li bng mt na bin th ng nng ca n bng. -T: 01689.996.187Din n: http://lophocthem.net- vuhoangbg@gmail.com BI DNG KIN THC N, LUYN THI I HC VT L - C HC VT RN62 A.4 / E . B.2 / E . C.4 / 3E .D.4 / 3E . Cu 10: Mt cht im dao ng iu ha xung quanh v tr cn bng vi bin 5 cm, tn s 5 Hz. Vn tc trung bnh ca cht im khi n i t v tr tn cng bn tri qua vtrcn bng n v tr tn cng bn phi l : A. 0,5 m/s. B. 2m/s. C. 1m/s. D. 1,5 m/s. Cu 11: Mt cht im dao ng iu ha xung quanh v tr cn bng vi bin 6 cm vchu k T. Thi gian ngn nht vt i t v tr c li - 3 cm n 3 cm lA. T/ 4.B. T /3. C. T/ 6.D.T/ 8. Cu 12: Nu chn gc ta trng vi cn bng th thi im t, biu thc quan h gia bin A (hay xm), li x, vn tc v v tn s gc ca cht im dao ng iu ha l : A. A2 = x2+2v2.B. A2 = v2+x2/2. C. A2 = x2+v2/2.D. A2 = v2+x22. Cu13:Vtdaongiuhaviphngtrnhos( ) x Ac t = + .thbiudinsph thuc ca vn tc dao ng v vo li x c dng no A. ng trn.B. ng thng. C. Elip.D. Parabol. Cu 14: Mt cht im c khi lng m dao ng iu ho xung quanh v cn bng vi bin A. Gi vmax , amax, Wmaxln lt l ln vn tc cc i, gia tc cc i v ng nng cc i cacht im. Ti thi im t cht im c ly x v vn tc l v. Cng thc no sau y l khng dng tnh chu k dao ng iu ho ca cht im ? A. T = dmaxm2.A2W. B. T = maxA2v. C. T = maxA2a. D. T = 2 22. A +xv. Cu15:Mtvtdaongiuhocsau1/8sthngnnglibngthnng.Qung ngvt i ctrong0,5s l16cm.Chngc thi gianlcvt quavtrcnbngtheo chiu m. Phng trnh dao ng ca vt l: A.8 os(2 )2x c t cm = + . B.8cos(2 )2x t cm = . C.4 os(4 )2x c t cm = . D.4 os(4 )2x c t cm = + . Cu 16: Mt vt dao ng iu ho vi chu k T v bin A. Tc trung bnh ln nht ca vt thc hin c trong khong thi gian 23T l A.92AT. B. 3AT. C. 3 32AT.D. 6AT. Cu 17: Hai cht im dao ng iu ho dc theo hai ng thng song songvi trc Ox, cnh nhau, vi cng bin v tn s. V tr cn bng ca chng xem nh trng nha