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VDB 1023
ENGINEERING MECHANICSCHAPTER 1: STATICS OF APARTICLECONDITION OF
EQUILIBRIUM, FREE-BODY DIAGRAMCarrol N C!"# Y"", $!DC%&%l a#'
E#&%ro#("#)al E#%#""r%# D"*ar)("#)U#%&"r+%)% T"#olo%
$ETRONAS
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COURSE LEARNINGOUTCOME CLO.
CLO Description
CLO1 Resolve a system of forces and apply the equilibrium
conditions
CLO2 Solve problem involving simple trusses and friction
CLO3 Calculate the geometrical properties of simple and complex
areas and so
CLO4 Analyze the dynamics of a rigid body
At the end of this course you shall be able to!
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RECA$ OF THE $REVIOUSLECTURE FORCE ??
FORCE VECOR
VECOR O!ER"#O$%
!O%##O$ VECOR
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HIGHLIGHT OF THISLECTURE S)/'"#)+ %ll " al" )o
E4*la%# a#' A**l5 "6/a)%o#+ o7 "6/%l%r%/(,
Dra a 7r""-o'5 '%ara( FBD.8
What, Why, and How of a Equation of Equi!i"#iu$
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EQUILIBRIUM OF A $ARTIC
• 9!"# )!" r"+/l)a#) o7 all 7or:"+ a:)%# o# a *ar;"ro, )!"
*ar)%:l" %+ %# "6/%l%r%/(8
• Newton’s First Law
• I7 )!" r"+/l)a#) 7or:" o# a *ar)%:l" %+ ;"ro, )!"*ar)%:l" %ll
r"(a%# a) r"+) or
• 9%ll r"(a%# :o#+)a#) &"lo:%)5 %7 or%%#all5 %# (
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• $ar)%:l" a:)"' /*o# 5 )!ror (or" 7or:"+- ra*!%:al +ol/)%o#
5%"l'+
:lo+"' *ol5o#- al"ra%: +ol/)%o#
• $ar)%:l" a:)"'/*o# 5 )o7or:"+- "6/al
(a#%)/'"-
+a(" l%#" o7
Co#'%)%o#+ o7 E6/%l%r%/( o7 $ar)%:l"
00
0
==
==
∑∑
∑
y x F F
F R
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Fr""-o'5 '%ara(+ ar" o#" o7 )!" (o+) %(*or)a#) )!%#7or 5o/ )o #o
!o )o 'ra a#' /+" 7or +)a)%:+ a#' o)+/
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A:)%&" 7or:"+ T!"5 a#) )o (o&" )!" *ar)%:l"R"a:)%&"
7or:"+ T!"5 )"#' )o r"+%+) )!" (o)%o
No)" C5l%#'"r (a++ ? @0
18 I(a%#" )!" *ar)%:l" )o " %+ola)"' or :/) 7r""7ro( %)+
+/rro/#'%#+8
A
38 I'"#)%75 "a:! 7or:" a#' +!o all #o#(a#%)/'"+ a#' '%r":)%o#+8
S!o all /##o#(a#%)/'"+ a#' or '%r":)%o#+ a+ &ar%al"+8
FC ( )*+- . /What
thi%0
FB
FD
30
28 S!o all )!" 7or:"+ )!a) a:) o# )!"*ar)%:l"8
FBD a) A
A
y
x
How%
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FREE-BODY DIAGRAMS
Space Diagram: A sketch showing
the physical conditions of the
problem.
Free-Body Diagram: A sketch
only the forces on the select
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P!an:
18 Dra a FBD 7or *o%#) A8
28 A**l5 )!" E-o7-E )o +ol&" 7or )!" 7or:"+ %# ro*"+ ABa#'
AC8
Given: The box weighs 550 N a
geometry is as shown.Find: The forces in the ropes
and AC.
Co*la#ar 7or:" +5+)"(
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FBD a) *o%#) FCFB
A
FD ( 223 .
y
x
30˚3
4
5
A**l5%# )!" +:alar E-o7-E a) A, " ")
→ ∑ F 4 ? FB :o+ 30 FC @. ? 0
→ ∑ F 5 ? FB +%# 30 FC 3. - 0 N ? 0
Sol&%# )!" ao&" "6/a)%o#+, " ")
FB ? @J N a#' FC ? 1J N
Co*la#ar 7or:" +5+)"(
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Co*la#ar 7or:" +5+)"(
18 Dra a FBD 7or $o%#) D828 A**l5 E-o7-E a) $o%#) D )o +ol&"
7or )!" /##o#+ F
FDE.8
38 #o%# FCD, r"*"a) )!%+ *ro:"++ a) *o%#) C8
Given: The mass of lamp is 20 kggeometry is as shown.
Find:The force in each cable.
Plan:
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Co*la#ar 7or:" +5+)"(
A**l5%# )!" +:alar E-o7-E a) D, " ")
↑ ∑ F5 ? FDE +%# 30 20 8J1. ? 0
→ ∑ F4 ? FDE :o+ 30 FCD ? 0
Sol&%# )!" ao&" "6/a)%o#+, " ")
FDE ? 32 N a#' FCD ? 3@0 N
FBD a) *o%#) D
FDE
FCD
D
W ( +3 /*410 .
y
x
30˚
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Co*la#ar 7or:" +5+)"(
A**l5%# )!" +:alar E-o7-E a) C, " ")
→ ∑ F4 ? 3@0 FBC +%# @ FAC 3. ? 0
↑ ∑ F5 ? FAC @. FBC :o+ @ ? 0
Sol&%# )!" ao&" "6/a)%o#+, " ")
FBC ? 2 N a#' FAC ? 2@3 N
FBD a) *o%#) C
FCD
!"0 N
FAC
C
y
x
45˚
FBC
3
45
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RECA$ OF THE LECTURE "xplain and Apply e#uations of e#uilibrium
and
$ra% a free&body diagram '()$*+
