LATIHAN TITIAN CEMERLANGCHAPTER 2 : FORCE AND MOTION

2 Diagram 2 shows a bag of cement of mass 35 kg on a ramp with 15o

slope to horizontal.Frictional force exerted between the bag and the ramp is 90.6 N.Rajah 2 menunjukkan sekampit simen di atas landas condong dengan kecondongan 15o terhadap ufuk. Daya geseran yang bertindak di antara kampit dan landas condong itu ialah 90.6 N.

Diagram 2 Rajah 2

(a) What is meant by frictional force?Apakah yang dimaksudkan dengan daya geseran?.................................................................................................................................................. (b) Calculate the resultant force parallel to the ramp.Hitungkan daya paduan selari dengan landas condong itu.

(c) Based on your answer in (b), explain what happens to the motion of the bag of cement?Berdasarkan jawapan anda dalam (b), terangkan apakah berlaku pada gerakan kampitsimen itu?…………………………………………………………….…………………………………..………………………………………………………………………………………………...

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9 Diagram 9 shows a ball placed onto smooth incline plane at point P. The ball is rolling down over he incline plane caused by gravitational potential energy. Point Q and point R are at the middle of the incline plane and at the ground respectively.Rajah 9 menunjukkan sebiji bola diletakkan di atas satah condong yang licin di titik P. Bola itu

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bergolek turun di atas satah condong itu disebabkan oleh tenaga keupayaan graviti. Titik Q dan titik R adalah masing-masing di tengah satah condong itu dan di tanah.

Diagram 9Rajah 9

(a) What is meant by gravitational potential energy? [Apakah yang dimaksudkan dengan tenaga keupayaan kenyal?

(b) (i) Using Diagram 9, compare the height of the ball, the gravitational potential energyof the ball, the velocity of the ball and the kinetic energy of the ball at point P andpoint Q.Deduce the relationship between the kinetic energy and the gravitational potentialenergy of the rolling ball.Menggunakan Rajah 9, bandingkan ketinggian bola itu, tenaga keupayaan kenyalbola itu, halaju bola itu dan tenaga kinetik bola itu pada titik P dan titik Q.Rumuskan hubungan di antara tenaga kinetik dengan tenaga keupayaan kenyal bolayang bergolek itu.

(ii) Name the physical principle involved in (b)(i). Namakan prinsip fizik yang terlibat dalam (b)(i).

(c) Explain what happens to the velocity of the ball when it reaches point R on the ground.Terangkan apa yang terjadi kepapa halaju bola itu apabila ia sampai pada titik R di atastanah.

(d) Based on the physical principle above, you are required to design a

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roller skate track.Using appropriate physics concept, explain the design of the roller skate track so that it canbe used to oscillate skate board continuously.Your answer should include the following aspects:Berdasarkan prinsip fizik di atas, anda diminta untuk merekabentuk trek papan peluncur.Menggunakan konsep fizik yang sesuai, terangkan rekabentuk trek papan peluncur yangdapat digunakan supaya papan peluncur boleh berayun berterusan.Jawapan anda hendaklah merangkumi aspek-aspek berikut:

(i) Shape of the trackBentuk trek

(ii) Slope of the trackKecondongan trek

(iii) Surface of the trackPermukaan trek

(iv) Safety.Keselamatan.

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7 Diagram 7 shows an electric motor lifting a 2.0 kg load. When the motor is switched on, the load moved through a height of 1.5 m in 2.5 s with constant speed. The currentflowing in the circuit is 1.7 A and the potential difference across the motor is 10.0 V.Rajah 7 menunjukkan sebuah motor elektrik sedang mengangkat satu beban 2.0 kg.Apabila motor itu dihidupkan, beban itu bergerak melalui ketinggian 1.5 m dalam 2.5 s dengan laju malar. Arus yang mengalir dalam litar ialah 1.7 A dan beza keupayaan merentasi motor itu ialah 10.0 V.

Diagram 7 / Rajah 7(a) State the changes in energy that occur when the motor is switched on.Nyatakan perubahan tenaga yang berlaku apabila motor itu dihidupkan.……………………………………………………………………………………… (b) Calculate,Hitung,(i) the electrical power supplied when the motor is lifting the load.kuasa elektrik yang dibekalkan semasa motor itu mengangkat beban.

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(ii) the output power of the motor when the load moved through a height of1.5 m in 2.5 s.kuasa output motor apabila beban itu melalui ketinggian 1.5 m dalam 2.5 s.

(iii) the efficiency of the electric motor.kecekapan motor itu.

(c) If some of the load is removed while the motor is still lifting the load, whatchange is observed on the ammeter? Explain your answer.Jika sebahagian daripada beban dikeluarkan semasa motor itu mengangkatbeban, apakah perubahan yang diperhatikan pada ammeter? Jelaskan jawapananda……………………………………………………………………………………………………………………………………………………………………………… (d) Suggest one way to increase the efficiency of the motor.Cadangkan satu cara untuk menambah kecekapan motor itu.………………………………………………………………………………………

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7 . Diagram 7 shows a spring.Rajah 7 menunjukkan satu spring.

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Diagram 7 Rajah 7

(a) When a load is attached to the spring ;Apabila satu beban dilekatkan pada spring ;

(i) What happen to the length of the spring?Apakah yang berlaku pada panjang spring?……………………………………………………………………………...

(ii) What is the energy stored in the spring?Apakah tenaga yang tersimpan dalam spring?……………………………………………………………………………...

(iii) If the number of load is increased, what will happen to the energy in 7 a(ii)?

Jika bilangan beban ditambah, apakah yang akan berlaku kepada tenaga di 7 a(ii)?

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(b) The initial length of a spring is 15 cm. When a load with mass 300g is attached to the spring, the length of the spring is 21 cm.

Panjang asal spring adalah 15 cm. Apabila beban berjisim 300g dilekatkan pada spring. panjang spring adalah 21 cm.

What is the length of the spring if a load with mass 500g is attached to the spring?

Berapakah panjang spring jika beban berjisim 500g dilekatkan pada spring?

(c) The spring in Diagram 7 is not suitable to be used as a spring cradle.

Suggest modifications to be done based on the characteristics given

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below.Spring dalam Rajah 7 tidak sesuai digunakan untuk spring buaian.Cadangkan pengubahsuaian-pengubahsuaian yang perlu dilakukan

berdasarkanciri-ciri yang diberi di bawah.(i) Arrangement of the springsSusunan spring…………………………………………………..…………………………

(ii) ReasonSebab……………………………………………………………………………... (iii) Stiffness of the springKekerasan spring……………………………………………………………………………... (iv) ReasonSebab……………………………………………………………………………...

8 Diagram 8 shows the graph of force against extension for three springs P, Q and R.Rajah 8 menunjukkan graf daya melawan pemanjangan bagi tiga spring P, Q dan R.

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Diagram 8 / Rajah 8

(a) (i) A law states that the extension of a spring is directly proportional to theforce applied if the elastic limit of the spring is not exceeded.Name this law.Suatu hukum menyatakan bahawa pemanjangan seutas spring adalahberkadar terus dengan daya yang dikenakan jika had kenyal tidak dilebihi.Nyatakan hukum ini.…......................................................................................................................

(ii) On the graph in Diagram 8, mark ' X ' at the elastic limit for each spring.Pada graf dalam Rajah 8, tandakan ' X ' pada had kenyal setiap spring.

(b) The spring stores energy when it is extended.Spring itu menyimpan tenaga apabila diregang.

(i) Name the energy stored in the spring when it is extended.

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Namakan tenaga yang disimpan dalam spring yang diregang.…...................................................................................................................... (ii) Calculate the energy stored in spring R when its extension is 8.0 cm.Hitung tenaga yang disimpan dalam spring R apabila pemanjangannya8.0 cm.

(c) The springs are to be used in a Newton balance to measure a maximum load ofmass 8 kg.Spring-spring tersebut akan digunakan di dalam neraca Newton untuk mengukurbeban maksimum berjisim 8 kg.

(i) What is the maximum weight of the load?Berapakah berat maksimum beban itu?…......................................................................................................................

(ii) Based on Diagram 8, choose two springs which are suitable to be used in theNewton balance specified above.Berdasarkan Rajah 8, pilih dua spring yang sesuai untuk digunakan didalam neraca Newton tersebut di atas.…......................................................................................................................

(iii) Which spring is the most suitable to be used in the Newton balance? Explainyour answer.Spring yang manakah paling sesuai untuk digunakan di dalam neracaNewton itu. Terangkan jawapan anda.…......................................................................................................................…......................................................................................................................

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9 Diagram 9.1 shows a stationary pistol on a smooth surface.Diagram 9.2 shows the pistol and bullet after the pistol has been fired by remotecontrol.Rajah 9.1 menunjukkan sebuah pistol pegun di atas permukaan licin.Rajah 9.2 menunjukkan pistol dan peluru selepas tembakan dilepaskan secara kawalanjauh.

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Diagram 9.1 / Rajah 9.1Diagram 9.2 / Rajah 9.2

(a) (i) What is the meaning of momentum?Apakah maksud dengan momentum?

(ii) State the total momentum of the pistol and bullet in Diagram 9.1Using Diagram 9.1 and Diagram 9.2, compare the total momentum beforeand after the bullet is fired.Using Diagram 9.2, compare the magnitude and direction of the momentumof the bullet and pistol.Name the physics principle that can be applied to the motion of the bulletand pistol.Menggunakan Rajah 9.1 dan Rajah 9.2, bandingkan jumlah momentumsebelum dan selepas peluru itu ditembak.Menggunakan Rajah 9.2, bandingkan magnitud dan arah momentum pelurudan pistol.Nyatakan prinsip fizik yang boleh diaplikasi kepada gerakan peluru danpistol itu.

(b) Describe, in terms of momentum, the propulsion of a rocket engine.Terangkan, dalam sebutan momentum, rejangan sebuah enjin roket.

(c) Diagram 9.3 shows a the structure of a jet engine for a small jet plane.

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Rajah 9.3 menunjukkan struktur sebuah enjin jet bagi sebuah kapal terbang jetyang kecil.

Diagram 9.3 / Rajah 9.3

You are required to give some suggestions to improve the design of the jet engineso that it can be used on a larger jet plane that travels at a higher speed.Using the knowledge on forces and motion and the properties of materials, explainthe suggestions based on the aspects labeled on Diagram 9.3Anda dikehendaki memberi beberapa cadangan untuk membaiki reka bentuk enjinjet itu supaya enjin jet itu boleh digunakan pada sebuah kapal terbang jet yanglebih besar dan bergerak lebih laju.Menggunakan pengetahuan tentang gerakan, daya dan sifat-sifat bahanterangkan cadangan itu yang merangkumi aspek-aspek yang dilabel pada Rajah 9.3.

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ANSWERS

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(a) 1 Force that oppose acted force forward.(b) 11F = Acted force - Frictional force= W CosӨ – Fr

= 350 Cos 75o – 90.6 // 350 Sin 15o

- 90.6= 0 N(c) 11Stationary.Balanced forces // Forces in equilibrium // Acted forceequal to frictional force.

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r 2No.9

(a) Energy caused by position from ground..(b)(i) The height of the ball at P > at Q

Gravitational potential energy of the ball at P > at QThe velocity of the ball at Q > at PThe Kinetic energy at Q > at P.The Kinetic energy increases as the gravitationalpotential energy decreases.

(ii) Principle of conservation of energy.(c) Velocity increases

Kinetic energy maximum / increasesBased on the principle of conservation of energy,gravitational potential energy is zero because changedto maximum kinetic energy.

(d) Semi circular curve shapedExchange between kinetic energy and gravitationalpotential energy easily.Increasing / decreasing slope slightlyEasily oscillates caused by changing of energy.Smooth surfaceEasily to moves // Reduce frictional force.Soft layer at the surfaceReduce impulsive force when landing / accident.Strong material // concrete of foundation of the track.Withstand to the high force caused by jumping andlanding.

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No.7

7(a) State the energy changes correctly - electrical energy to (gravitational) potential energy(b) (i) Correct substitution - 1.7 x 10Correct answer and correct unit- 17 W(ii) Correct substitution

2 x 10 x 1.52.5

Correct answer with correct unit- 12 W (iii) Correct substitution 1

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x100%

Correct answer with correct unit- 70.6 % (c) State the change on the ammeter correctly - ammeter reading decreasesGive explanation correctly 1- less work done // less power required(d) Give one suggestion correctly- lubricate the moving parts to reduce friction

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7(a) (i) Length increases/ longer (ii) Elastic potential energy (iii) Increase

(b) Extension ( 21-15 ) cm= 6 cm300g-------6 cm100g-------2 cm500g--------2 x 5 = 10 cm

Length of spring = 15 + 10 = 25 cm

(c) (i) Parallel (ii) Load is shared equally among the spring / can support higher load (iii) Stiffer/harder (iv) Spring constant is higher/greater/bigger /. Not easily broken / able tosupport higher weight

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r 2No. 8

8(a) (i) Name the law correctly 1- Hooke’s Law(ii) Mark a cross on each line correctly - All correct (2 marks)- 1 or 2 correct (1 mark)

(b) (i) State the energy correctly - Elastic potential energy(ii) Determine the force correctly - From the graph, F = 60 NCorrect substitution- ½ (60)(8)// ½ (60)(0.08)

Correct answer with correct unit - 240 N cm // 2.4 J // 2.4 N m(c) (i) State the maximum weight correctly - 80 N(ii) Name the two springs correctly 1 + 1- Spring P- Spring Q(iii) Give the choice correctly - Spring QGive the explanation correctly - More sensitive//smaller force constant

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No. 9

(i)- Product of mass and velocity / /momentum = mass x velocity 1(ii) State the total momentum in Diagram 9.1 correctly- ZeroCompare the total momentum correctly- Total momentum before the bullet is fired = total momentum

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after the bullet is fired.

Compare the magnitude of the momentum of the bullet andpistol correctly- Equal

Compare the direction of the momentum of the bullet andpistol correctly- Opposite

Name the physics principle correctly- Principle of Conservation of Momentum

(b) Describe the propulsion of a rocket engine correctly- Liquid oxygen and liquid hydrogen/fuel is pump into thecombustion chamber for combustion- The exhaust gas is ejected out of the rocket nozzle at high speed.- The ejected exhaust gas at high speed has a large momentum.- According to the Principle of Conservation of Momentum, therocket acquires a large momentum forward

(c) State aspect of blade correctly 1- Using bigger blades/increase the number of blades/increase thespeed of bladeState reason for aspect of forces and motion correctly- Increase the air intakeState aspect of material of blade correctly- Blade made of strong materialState reason for aspect of material of blade correctly- Can withstand strong pressure/it will not break easily

State aspect of fuel injector correctly- Increase the number of fuel injectors//add more fuel injectorsState reason for aspect of fuel injector correctly- More fuel to be burnt to produce greater thrust

State aspect of combustion chamber correctly- Increase the size of the combustion chamberState reason for aspect of combustion chamber correctly- More space for the fuel to be burntState aspect of nozzle correctly- Decrease the diameter of the nozzle

State reason for aspect of nozzle correctly- Exhaust gas ejected at higher velocity/higher momentum

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