chapter 2 force and motion (answer)
TRANSCRIPT
-
8/17/2019 Chapter 2 Force and Motion (Answer)
1/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
1
2. FORCE AND MOTION
2.1 ANALYSING LINEAR MOTION
Distance and displacement
1. Types of physical quantity:
has only a magnitude(i) Scalar quantity: ………………………………………………………………….has both magnitude and direction
(ii) Vector quantity: …………………………………………………………………
2. The difference between distance and displacement:length of the path taken
(i) istance: …………………………………………………………………………distance of an object from a point in a certain direction
(ii) isplacement: ……………………………………………………………………
!. istance always lon"er than displacement.
#. $%ample: The followin" dia"ram shows the location of &ohor 'ahru and esaru.
ou can trael by car usin" e%istin" road ia *ota Tin""i+ or trael by asmall plane alon" strai"ht path.
,alculate how far it is from &ohor 'ahru to esaru if you traeled by:
a. The car
b. The plane*ota Tin""i
#1 -m ! -m
Solution:&ohor 'ahru
/0 -m esaru
a. by car #1 !
3# -m
b. by plane /0 -m
The path traeled by the plane is shorter than traelled by the
car.
So+ istance 3# -m
isplacement /0 -m
4ands5on 6ctiity 2.2 p" 10 of the practical boo-.
7dea of distance and displacement+ speed and elocity.
Speed and velocity
! Speed is ..……the
…d
…ist
…an
…ce
…tra
…"e
…le
…d p
…er
…un
…it
…tim
…e
…or
…ra
…te
…of
…ch
…an
… ge
…of
…di
… sta
…nc
…e
…………
2! Velocity is: ..…the
… sp
…ee
…d
…in
…a g
…i"
…en
…dir
…ec
…tio
…n
…
or …
ra…
te…
of…
ch…
an…
ge…
of …
di…
spl …
ac…
em…
en…
t #
………...
$!6era"e of speed: …
to…
ta…
l d …
ist …
an…
ce…
tra…
"e…
le…
d%…
s & …
m'…
%…
"…
(
s……
m…
s………………………
-
8/17/2019 Chapter 2 Force and Motion (Answer)
2/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
2
#
time taken% t &s' t
4!6era"e of elocity:
d …
isp…
la…
cem…
e…
nt%…
s…
&m…
' %……
" (……
s m…
s…………………………………... )ime taken% t &s' t
-
8/17/2019 Chapter 2 Force and Motion (Answer)
3/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
2. 6cceleration is+
*!$%ample:
6n aero plane flies from 6 to '+ which is located !00 -m east of 6. 8pon reachin" '+ the
aero plane then flies to ,+ which is located #00 -m north. The total time of fli"ht is #hours. ,alculate
i. The speed of the aero plane
ii. The elocity of the aero plane
Solution:
6 !00 -m
C
#00 -m
'
,
#00 -m
i! +peed ( ,istance
)ime
( $-- . 4--4
( /* km h#
ii! "elocity ( displacement
time
&,etermine the displacement denoted
by 0C and its direction'
= . 500 .
6 '
!00 -m
4( 2* km h
#&in the direction of -*$
- '
Acceleration and deceleration
1. Study the phenomenon below9
0 m s51 20 m s
51
)he "elocity of the carincreases!
#0 m s51
bseration: ………………………………………………………………………………the rate of change of "elocity
………………………………………………………………………. Final "elocity 1 initial "elocity
Then+ a Or, a = v – u
)ime of change t !. $%ample of acceleration9
t 2 s t 2 s
6 ' ,
-
8/17/2019 Chapter 2 Force and Motion (Answer)
4/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
0 m s51 20 m s51 #0 m s51
-
8/17/2019 Chapter 2 Force and Motion (Answer)
5/108
. . . . . . . .
.%. . . . . . .
. . .……………………………………………………………………………………..
. . . . .
. . . . . . . .
JPN Pahang
20 – 02
= 10 m s-2
Physics Module Form 4Chapter 2 : Force and Motion
,alculate the acceleration of car9
i' from 6 to ' a 0 ( 2- 1 - ( - m s#2
2
ii' ;rom ' to , a C ( 4- 1 2- ( - m s2
3hen the "elocity of an object decreases% n calculations% a 3ill #. eceleration happens ...…………………………………………………………………
be negati"e………………………………………………………………………………………………
. $%ample of deceleration9
6 lorry is moin" at !0 m s51+ when suddenly the drier steps on the bra-es and it stop
seconds later. ,alculate the deceleration of lorry.
0ns3er : " ( - m s# % u ( $- m s# % t ( * s
Analyzin o! motion
)hen % a ( - 1 $- ( #5 m s#
2 *
!
-
8/17/2019 Chapter 2 Force and Motion (Answer)
6/108
0cceleration% then deceleration
-
8/17/2019 Chapter 2 Force and Motion (Answer)
7/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
# s ( ;--
a (
(
(
(
u
.etermination of elocity
. . . . . . .
.……………………………………………………………………………………..
(i)
2!5 cm / 9 -!-2 ( -!4 s
displacement ……………………… time ………………………………..
Velocity+ 2!5 (
-
8/17/2019 Chapter 2 Force and Motion (Answer)
8/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
s ( ;--
( ;-- m
-
8/17/2019 Chapter 2 Force and Motion (Answer)
9/108
;i"ur 2.1e
$%ample 2 : 6 an that is traelin" with elocity 1/ m s51 decelerates until it comes to rest.
7f the distance traeled is ? m+ calculate the deceleration of the an.
gi"en : u ( 5 m s# % " ( -&rest' % s ( ; m a (
= "2 ( u2 . 2 as
-2 ( 5 2 . 2 a&;'
a ( #5 ms#2
E%ercise 2.&
1. ;i"ure 2.1 shows a tape chart
consistin" of 5tic- strip. escribe
-
8/17/2019 Chapter 2 Force and Motion (Answer)
10/108
/
s final ( sinitial 1 s
( ;- 1 5-
( 2- m
-
8/17/2019 Chapter 2 Force and Motion (Answer)
11/108
Araph analysis:
ANA'(SIN) MOTION )RA*+S
0m 100m 200m !00m #00m 00m displacement
0s 10s 20s )he ob! je
0cst mo"es 3
#i0t sh uniform "
e0lo
scity
for tt im
seeconds!
0fter t secoinnd t sh %eth foer ombo je f c g t r r ae ptuhr cna sl t l oed or aig minot & ir oen"e g r r sae p 'h3 s ith
The data of the motion of the car can beu pnr if eosr emnte"de…loc…ity…………………………….
T"e displacement,time )rap" )otal displacement is 8ero
a' displacement (m) Araph analysis:
… ?…nr ia f …o pr h…mis…d 6is…u pala…d crae…mtic…en fo…t r am…ll t …he…tim…e…………………………
!
…? ,…r ia s… p phla… g cr e…amd …eiennt …t in…(cr …e"ael …
soec s…it 3 y…it (h…-ti…me…!
………………………
s) …) …?hr e…ao p…bh je… g cr t a..id . s…ie st n…at tii…onnc…
r aer a… y soe…r s iu… snni… f oot r …mm…oly"…ing …………………
b'displacement (m)
)he object mo"es 3ith increasing "elocity 3ithuniform acceleration!
… ,…is. p.…la…cem…e…nt …inc…re…ase… s …un…
ifo…rm…ly…………………………
…?…ra… ph… g …ra…die…nt …is… fi9…
ed ……………………………………… time (s)…) …he…o.b… je…ct …
mo…"e…3…ith…un…ifo…rm…"…elo…ci…ty ………………………
c' displacement (m) Araph analysis:
…….……………………………………………………………
…………………………………………………………………
time (
time (s)
-
8/17/2019 Chapter 2 Force and Motion (Answer)
12/108
..…………………………………………………………………
d' isplacement (m) Araph analysis:
…………………………….………………………………………
……………………………………………..………………………
time (s) ………………………………………………………………………
…………………………………………………………………
-
8/17/2019 Chapter 2 Force and Motion (Answer)
13/108
e' displacement (m) Araph analysis:
…?r
…ap
…h i
… s 6
…ua
…dr
…at
…ic
… for
…m!
………………………………..
… ,i… spl …ac…em…en…t i…nc…rea… se… s 3…it …h
t …im…e! ……………………..
…?…rap…h… gr …ad …ien…t d …ec…re…ase… s u…n
fo…rm…ly …………………..
time (s)
…)h…e o…bj…ect …m…o"…es…3i…th…de…cre…as
in… g "…el …oci…ty%…3…ith…un…ifo…rm..deceleration!
f' displacement (m) Araph analysis:
6 '@0
…( u
…ni
… for
…m
…"e
…lo
…cit
… y &
… po
… siti
…"e
… 1
…mo
…"e
…a…
hea…
d'……………..
…… 0
…
…(
…"el
…oc
…ity
…is
… 8e
…ro
…&re
… st
… '
………………………..
, time (s)
T"e velocity,time )rap"
… C
…(
…u
…nif
…or
…m "
…el
…oc
…ity
…&n
…eg
…ati
"e…
1…
re"…
er …
se'………………
a) > m s51 Araph analysis:
No cha…ng …e …in …"e…loc…
ity………………………………………
…..
…..
Aero gradient the object mo"es 3ith a constant "elocity or
the acc…el …era…ti…on…is… 8e…ro!
……………………………………
)he area under the graph is e6ual to the displacement of th
mo"ing object :…………… s (…"… 9 …t
b) …> m s51 Araph analysis:
…………………………………
…..
…
ts "e…
lo…
cit …
y i…
ncr …
ea…
se…
s u…
nif …
or …
ml …
…………..……………)he graph has a constant gradient
)he…
ob…
jec…
t m…
o…
"es…
3…
ith…
a…
un…
ifo…
-
8/17/2019 Chapter 2 Force and Motion (Answer)
14/108
rm
…a
…cc
…ele
…ra
…tio
…n
…………
)he area under the graph is e6ual to the displacement%
s of the mo"ing object : s ( > & " 9 t'
c) (m s51) Araph analysis:
)he object mo"es 3ith a uniform acceleration for t s…………………………………..…………………. 0fter t s% the object decelerates uniformly &negati"e gradien………………………………………………………until it comes to rest!………………………………………………………)he area under the graph is e6ual to the displacement of the
t1 t2 t (s)mo"ing object : s ( > "t 2
-
8/17/2019 Chapter 2 Force and Motion (Answer)
15/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
R
0 t>
d) (m s51) Araph analysis:)he shape of the graph is a cur"e...…………………………………..………………..
ts "elocity increases 3ith time!………………………………………………
)he gradient of the graph increases!……..
t (s)
)he object mo"es 3ith increasing acceleration!………………………………………………………
)he area under the graph is e6ual to the total displacement oth
…e
…mo
…"i
…ng
…ob
… je
…ct!……………………………………
.……………………………………………………...
)he shape of graph is a cur"ee) (m s51) Araph analysis:
ts "elocity increases 3ith time!………..…………………………..………………..
)he gradient of the graph decreases uniformly!……….……………………………………
)he object mo"es 3ith a decreasing acceleration!………..
)he area under the graph is the total displacement of the
m…
o"…
in…
g o…
bj…
ect …
! ………………………………………
t (s) ………………………………………………………
E%amples ………………………………………………………
1. s>m,alculate:5&i' Velocity o?ie"r en B:++ C@P = (an2d- = mS + @B ( 2- m + @
- m
20 P Q
&ii'isplacement
Solution :
+ @+ ( # - m
t @P ( 2 s t PB ( $ s t B ( 2 s t + ( s
20 −1 0 − 20 −1
10&i' D @P (
2
=10m
s
D B ( = −10ms2
O R D +(
-10 −
0= −10ms
−1
0 2 # / ? t>s
1
&ii' + ( #-m
510 S
2. >m s51
10,alculate:5
(i) acceleration+a oer B+ BC and C=
(ii) isplacement
P Q ?i"en : D @ ( - m s# % D P ( - m s
# %Solution :D B ( - m s
# D ( - m s#
t @P ( 4 s t PB ( 4 s t B ( 2 s10 − 0 − 10 −10
0 2 #
-
8/17/2019 Chapter 2 Force and Motion (Answer)
16/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
/ ? 1 &i' a@P(
s
4
aB(
= 2.5ms2
a PB(4
- − -= −*!- ms
−2
2
= 0
ms−2
? 1&ii' + (
(4
2
+10)
(10)
= 70.0m
-
8/17/2019 Chapter 2 Force and Motion (Answer)
17/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
10
0
510
2 #t>s
t>s
10
0
510
2
#
O
E%cercise 2.2
1. (a) s>m (b) s>m (c) s>m
t>s
;i"ure 2.21
escribe and interprDte the motion of a body which is represented by the displacement
time "raphs in ;i"ure 2.21a' )he body remains in rest * m at the back of initial point
b' )he body start mo"e at - m infront of the initial point% then back to initial
point in 2 s! )he body continue it motion back3ard - m!!)he body mo"e 3ith uniform "elocity!
c' )he body mo"e 3ith inceresing it "elocity!
2. escribe and interpret the motion of body which is represented by the elocity5time
"raphs shown in fi"ure 2.22. 7n each case+ find the distance coered by the body and itsdisplacement
(a) >m s51 (b) >m s51
t>s t>s
;i"ure 2.22
&a' )he body mo"e 3ith uniform "elocity % * m s# back3ard!
&b' )he body start it motion 3ith - m s# back3ard and stop at initial point in 2 s% then continue it motion for3ard 3ith increasing the "elocity until
- m s# in 2 s!
3
5
5
-
8/17/2019 Chapter 2 Force and Motion (Answer)
18/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
……………………...
…………………………….
-NDERSTANDIN) INERTIA
Idea o! inertia 0 pillion rider is hurled back3ards 3hen the motorcycle starts to mo"e!
1. ……………………………………………………………………………………………… us passengers are thrust for3ard 3hen the bus stop immediately!
2. ……………………………………………………………………………………………… Earge "ehicle are made to mo"e or stopped 3ith greater difficulty!
!. ………………………………………………………………………………………………
4and5on actiity 2. in pa"e 1? of the practical boo- to "ain an idea of inertia
#. Eeanin" of inertia :)he inertia of an object is the tendency of the object to remain at rest or% if mo"ing% to…………..………………………………………………………………………………….
continue its uniform motion in a straight line………………………………………………………………………………………………
Mass and inertia
1. =efer to fi"ure 2.1# of the te%t boo-+ the child and an adult are "ien a push to swin".
&i'which one of them will be more difficult to be moed
0n adult
&ii'which one of them will be more difficult to stopF
0n adult
2. The relationship between mass and inertia : ……………………………….………………)he larger the mass% the larger its inertia!……………………………………………..
ha"e the tendency to remain its situation either at rest or in!. The lar"er mass ………………………………………………………………………….
mo"ing!………………………………………………………………………………………………
E!!ects o! inertia 0pplication of inertia
1. Bositie effect : ………………………………………………………………………… ,rying off an umbrella by mo"ing and stopping it 6uickly!
(i) ……………………………………………………………………………………… uilding a floating drilling rig that has a big mass in order to be stable and safe!
(ii) ………………………………………………………………………………………)o tight the loose hammer
(iii) ………………………………………………………………………………………
e should take a precaution to o"oid the effect!2. Ge"atie effect : …………………………………………………………………………. ,uring a road accident% passengers are thrust for3ard 3hen their
(i) ……………………………………………………………………………………...car is suddenly stopped!
…………………………………………………………………………… Passengers are hurled back3ards 3hen the "ehicle starts to mo"e and are hurled for3ard
………..3hen it stops immediately!
(ii) ……………………………………………………………………………………… 0 person 3ith a hea"ierGlarger body 3ill find it mo"e difficult to stop his mo"ement!
0 hea"ier "ehicle 3ill take a long tim10e to stop!
-
8/17/2019 Chapter 2 Force and Motion (Answer)
19/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
………………………………………………………………………………………
(iii) ………………………………………………………………………………………
………………………………………………………………………………………
(i) ………………………………………………………………………………………
E%ecise 2.
1. Hhat is inertiaF oes 2 -" roc- hae twice the inertia of 1 -" roc-F netia is the tendency of the object to remain at rest or% if mo"ing% to continue its uniform………………………………………………………………………………………………motion in a straight line!………………………………………………………………………………………………Hes% the inertia increase 3ith the mass increased!………………………………………………………………………………………………
2.
;i"ure 2+!
6 wooden dowel is fitted in a hole throu"h a wooden bloc- as shown in fi"ure 2.!1.
$%plain what happen when we
(a) stri-e the top of the dowel with a hammer+
0 3ooden block mo"e up of a 3ooden do3el!……………………………………………………………………………………… 0 3ooden block has inertia to remains at rest!………………………………………………………………………………………
(b) hit the end of the dowel on the floor.
)he 3ooden block mo"e do3n3ard of a 3ooden do3el!……………………………………………………………………………………… 0 3ooden block has inertia to continue it motion!……………………………………………………………………………………
ANA'(SIN) MOMENT-M Idea o!
moment$mit has momentum!
1. Hhen an obIect is moin"+ …...…………………………………………………………depends on its mass and "elocity!
2. The amount of momentum ...……………………………………………………………as the product of its mass and its "elocity% that is
Momentum% p ( m 9 " nit( kg m s#11
-
8/17/2019 Chapter 2 Force and Motion (Answer)
20/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
mv
bb
!. Eomentum is defined…………………………………………………………………….
………………………………………………………………………………………………
Conservation o! moment$m
mg
m v v = 0b
bg
Momentum ( m "b b
Startin" position beforeshe catches the ball
(m m ) b "
vb&g
ecei"ing a massi"e
ball Momentum( &m .m '"
b g bIg
vg
" Momentum ( m
b bStartin" position m"
before she throws
the ball Momentum (# m "
)hro3ing a massi"e ball g g
T"e principle o! conservation o! moment$m / ………………………………………………… n t he absence of an e9ternal force% the total momentum of a system remains
……………………………………………………unchanged!
………………………………………………………………………………………………………)he colliding objects mo"e separately after collision!
1. $lastic collision .…………………………………………………………………………..
u1
m1 u2 2
m2 m1m2
12
-
8/17/2019 Chapter 2 Force and Motion (Answer)
21/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
Momentum : mu . m2u2 ( m" . m2"2
-
8/17/2019 Chapter 2 Force and Motion (Answer)
22/108
1!
'efore collision after collision
)he colliding objects mo"e together after collision!2. 7nelastic collision :………………………………………………………………………...
u1
m1 u2 0m2
1
m2
'efore collision after collision Momentum : mu . m2u2 ( &m . m2 ' "
)he objects in"ol"ed are in contact 3ith each other before e9plosion and are!. e%plosion : s
…ep
…ara
..t .e..d
…a…
fte…
r t …
he…
e9…
plo…
si…
on…
!
…………………………………………...
(m1 m2)+ u 0 1 2
m2
Momentu'
mef
:or
& em
e%. plos
mio
'nu (
m " # m " after e%plosion 2 " 2 2
$%ample 1 :
,ar 6 ,ar '
,ar 6 of mass 100 -" traelin" at !0 m s51 collides with ,ar ' of mass 30 -" traelin" at 20m s51 in front of it. ,ar 6 and ' moe separately after collision. 7f ,ar 6 is still moin" at 2 ms51 after co?lil"iseinon:+mdet(erm-i-nekg the eloc % iuty (of $,-amr ' s#after collision#.
Solution : 0
0
u ( 2- m s# % " ( =
% " 0 ( 2* m s
% m (
-
8/17/2019 Chapter 2 Force and Motion (Answer)
23/108
,ar 6 of mass 100 -" traelin" at !0 m s51 collides with ,ar ' of mass 30 -" traelin" at 20
m s51 in front of it. ,ar 6 is pulled by ,ar ' after collision. etermine the common elocity of ,ar 6 and ' after collision.
?i"en : m 0 ( -- kg % u 0 ( $- m s# % m (
-
8/17/2019 Chapter 2 Force and Motion (Answer)
24/108
Stationary obIect
3eight% 3 ( mg
FK
Idea o! !orce
1. Hhat will happen when force act to an obIectF Force can make an object………………………………………………………………………………………………
! Mo"e 2! +top the mo"ing ………………………………………………………………………………………………!. Change the shape of the object 4! 7old the object at rest
………………………………………………………………………………………………
Idea o! 1alanced !orces
1. 6n obIect is said to be in balance when it is:! n a stationary state
………………………………………………………………………………………………2! Mo"ing at uniform "elocity
………………………………………………………………………………………………
2. Stationary obIect Normal reaction% N
……………………………… e%planation : Magnitude ( but acts in an opposite………………………………………………direction to the 3eight!………………………………………………& object is in e6uilibrium '……….……………………………………..
…………………………………………
!. 6n obIect moin" with uniform elocity Normal reaction% N …………………………….. e%planation :
Frictional force Force% F Force % F ( Friction…..……………. …………… ……………………………………………..
………………..
esultant ( F 1 Friction……………………………
( - &object is in e6uilibrium'
3eight% 3 ( mg L9amples :……………………………………………..
!0 car mo"e at constant "elocity!……………………………… ………..…………………………………….
2!0 plane flying at constant "elocity!……………………………………
……….. ……………………………3hen it is mo"ing in acceleration!
………………..
esultant forceIdea o! $n1alanced !orces)he ball mo"e in acceleration
1. 0 body is said to be in unbalanced!!……………………………………………………because the forces act are not balanced! F
2. ……………………….. $%planation9 FK
F …………
……………………………………+o% the ball mo"e in F direction
-
8/17/2019 Chapter 2 Force and Motion (Answer)
25/108
………………………………………………
………………………………………………
……… …….. ………………………………………………
Relations"ip 1eteen !orces3 mass and acceleration 4F 5 ma6
L9periment 2!2 page 2
constant force.
1. =efer to the result of e%periment 2.2 and 2.!+it is found that a ∝ F 3hen m is constant and a ∝ Gm 3hen F is constant!……………………………………………………………………………………………)herefore% a ∝ FGm
……………………………………………………………………………………………… Fr …om a ∝ FGm%
………… F …
∝…m…a…………………………………………………………………………
…)h…ere… fo…re%… F …(…km…a ……k …(c…on… sta…nt …(…
…………………………………………………
……
………………………………………………………………………………………………
2. 1 newton (; 1 G) is defined as the force required to produce an acceleration of 1 m s52
(a1 m s52) when its actin" on an obIect of mass 1 -" ( m 1 -") F ( ma…………………………………………………………………………………………
!. $%ample 1 : ,alculate ;+ when a ! m s52 dan m 1000 -" F ( ma
F ( &---'
&$' F ( $---
N
$%ample 2 :m 2 -"m 2 -"
; 200 G; 200 G
E%ercise 2.7
So+
-
8/17/2019 Chapter 2 Force and Motion (Answer)
26/108
,alculatetheacceleration+a of anobIect.
F
(
ma
2
--
(
2
*
a
a (
;!-
ms#2
-
8/17/2019 Chapter 2 Force and Motion (Answer)
27/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
1. 6 trolley of mass !0 -" is pulled alon" the "round by horiJontal force of 0 G.
The opposin" frictional force is 20 G. ,alculate the acceleration of the trolley.
m ( $- kg % F ( *- N % F f ( 2- N % a ( =
F 1 F f ( ma % *- 1 2- ( $- a
a ( !- m s2
2. 6 1000 -" car is traellin" at @2 -m h51 when the bra-es are applied. 7t comes to a stop in
a distance of #0 m. Hhat is the aera"e bra-in" force of the carF
m ( --- kg % u ( /2 km h# % " ( -% s ( 4- m% F ( = Note : u ( /2 km h# (2- m s#
F ( ma% "2 ( u2 . 2as
( --- 9 *!- - ( 2-2 . 2a&4-'
( *---!- N a ( *!- m s2
ANA'(SIN) IM*-'SE AND IM*-'SI8E FORCE
Imp$lse and imp$lsive !orce)he change of momentum
1. 7mpulse is ……………………………………………………………………………….)he large force that acts o"er a short period of time during collision
2. 7mpulsie force is ………………………………………………………………………and e9plosion!
………………………………………………………………………………………………
!. ;ormula of impulse and impulsie force:
=efer+ ; ma
F ( m" 1 mu %
t
t is kno3n that a ( & " 1 u ' G t
)herefore% F ( m& " 1
u' t +o% Ft ( m" 1 mu % nit ( N s
Ft is defined as impulse% 3hich is the change in momentum!
Ft ( m" 1 mu nit : ne3ton &N' F is defined as impulsi"e force 3hich is the rate of change of momentum o"er the
short per *io& d -o ' f t #ime*&-'' -- ( -- N
( -- Ns $%ample 19 u
wall
7f 9 u 10 m s51 + 5 10 m s51 + m -" and t 1 s
7mpulse+ ;t and impulsie force+ ;
*&-' # *&-'' -- ( *- N $%ample 29 u
( -- Ns 2
mpulsi"e force % F∝
G t
1@
)herefore% F decreases 3hen the time of collision increases & refer to e9amples '
-
8/17/2019 Chapter 2 Force and Motion (Answer)
28/108
1?
Hall with a soft surface
7f 9 u 10 m s51 + 5 10 m s51 + m -" and t 2 s
7mpulse+ ;t and impulsie force+ ;
#. The relationship between time of collision and impulsie force.
………………………………………………………………………………………………
………………………………………………………………………………………………
E%ercise 2.9
1. 6 force of 20 G is applied for 0.? s when a football player throws a ball from the
sideline. Hhat is the impulse "ien to the ballF
F impulse ( Ft
( 2- 9 -!;
( 5!- Ns
2. 6 stuntman in a moie Iumps from a tall buildin" an falls toward the "round. 6
lar"e canas ba" filled with air used to brea- his fall. 4ow is the impulsie forcereducedF
! 0 large can"as bag 3ill increase the time of collision!
2! hen the time of collision increase the impulsi"e force 3ill decrease!
:EIN) A;ARE OF T+E NEED FOR SAFET( FEAT-RES IN 8E+IC'ES
-
8/17/2019 Chapter 2 Force and Motion (Answer)
29/108
Crash resistant door pillars
Anti-lock brakesystem A!"#
bumpers
$ein%orced passen&er compartment
'ead rest
(indscreen
Crumple )ones
*raction control Air ba&s
13
Safety features in vehicles
Importance o! sa!ety !eat$res in ve"icles
force 3ill be decreased!# )he passengerKs space made by the strength materials!
E%ercise 2.< : )o decrease the risk trap to the passenger during accident!
1. '# O y eues pina"n pahiyr sbicas g caot nt chee pitns+ f ero%n pt laoin f
d thae shmbiodaif r id caatniod nisnto frothnet o b f us path ssaetnh g eelprsto improe that
safety of passen"ers an:d 0wct i slla b seamcour sehcioonm f f oor rtt ah beleh.ead and bodyin an accident and thus pre"ents injuries to the dri"er and passengers!
# +hatter#proof 3indscreen
: Pre"ents the 3indscreen from shattering!
Sa!ety !eat$res Importance
Badded dashboard ncreases the time inter"al of collision so the impulsi"e force
produced during an impact is thereby reduced
=ubber bumper 0bsorb impact in minor accidents% thus pre"ents damage to the car!
Shatter5proof windscreen Pre"ents the 3indscreen from shattering
6ir ba" 0cts as a cushion for the head and body in an accident and thus
pre"ents injuries to the dri"er and passengers!
Safety seat belt
Pre"ents the passengers from being thro3n out of the car! +lo3s
do3n the for3ard mo"ement of the passengers 3hen the car stops abruptly Gsuddenly!
# )he absorber made
Side bar # i M n add oeor bs y
the soft ma
by the elastic materia P :re) "oenat b s sothr eb cthoellae p ff seect oo f f thime fr aocnt t & ahned nt baamcak no ' f d t uhr einc g ar it inmtoo"t ihne gtear si sael no g f ebr ucmom pe pr artment! 0lso gi"es good protection
-
8/17/2019 Chapter 2 Force and Motion (Answer)
30/108
………………………………...
fallin
g
the object is said to be free
is kno3n as acceleration due to gra"ity!
on the strength of the gra"itational field
! the gra"itational field of the
earth! is on the force of gra"ity!
as the gra"itational force acting on a kg mass!
! g ( F ! 3here% F : gra"itational force
m m : mass of an object
g (
-NDERSTANDIN) )RA8IT(that an object of mass kg 3ill e9perience a gra"itational force of
,arry out hands5on actiity 2.? on pa"e ! of the practical boo-.
Acceleration d$e to ravity.
! 6n obIect will fall to the surface of the earth because t pulled by the force of
gra"ity! +olution : F ( mg ( &5-a ' s & e
-
8/17/2019 Chapter 2 Force and Motion (Answer)
31/108
/. This means …………………………………………………………………………………
…………..
@. $%ample 1. ,an you estimate the "raitational force act to your bodyF
mass /0 -"+ " 3.? G -"51+ ; F
$%ample 2+
6 satellite of mass /00 -" in orbit e%periences a "raitational force of #?00 G. ,alculatethe "raitational field stren"th.
$%ample !+
6 stone is released from rest and falls into a well. 6fter 1.2 s+ it hits the bottom of the
well.(a) Hhat is the elocity of the stone when it hits the bottomF
(b) ,alculate the depth of the well.?i"en : u ( - ms# % t ( !2 s% a ( g (
&a' " ( = " ( u . at
( - . &
( !/5 ms#
&b' ,epth ( s ( = s ( ut . > at 2
( &-'&!2' . > &
( /!-*5 m
;ei"tas the gra"itational force acting on the object!
1. The wei"ht of an obIect is defined ……………………………………………………..
2. ;or an obIect of mass m+ the wei"ht can be calculate as :3eight% ( mg
3here% g ( acceleration due to gra"ity!
$%ample : The mass of a helicopter is /00 -". Hhat is the wei"ht of the helicopter
when it land on the pea- of a mountain where the "raitational field is
3.@? G -"51F ( mg
( 5-- 9
-
8/17/2019 Chapter 2 Force and Motion (Answer)
32/108
( *; 5; N
-
8/17/2019 Chapter 2 Force and Motion (Answer)
33/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
force% F
t G s
E%ercise 2.=
1. S-etch the followin" "raphs for an obIect that fallin" freely.
(a) isplacement5time "raph+
(b) Velocity5time "raph(c) 6cceleration5time "raph
&a' s G m &b' " G m s# &c' a G m s2
2. The followin" data was obtained from an e%periment to measure the acceleration due to
"raity.
Eass of steel bob 200 "+ distance coered !.0 m+ time of fall 0.@3 s.
,alculate the acceleration due to "raity of steel bob.Aie the e%planation why your answer different with the constant of "raitational
acceleration+ " 3.? m s52.
m t i( s i2n-a- s g tationary s ( sta$t !e- m t ( -!/< s u ( - g ( =
t i( s m
-!o2"i
k n g
g 3ith uniform "elocity
s ( ut . N >or g mt a
2
l reaction% Normal reaction% $!- ( - &-!/)he ans3er less
t ehia g
nht
t %h
e c
(om
ns g
tant because o3 f t
eh
ie gh
at i %r
fr (
icm
ti g
onal
force!
IDEA OF E>-I'I:RI-M FORCES Magnitude of ( Magnitude of ( mg cos θ
6n o bIeacntd is inaec#ts$iilni1or pi p$om siwtehd einre:ction! 0nd acts in opposite direction!
1. +o%…… …es…ult …an…t fo…rc…e (… … 1 … …(…-………+o… %…es…ult …an…t f …orc…e …( m… g …co… s …θ
& object in e6uilibrium ' & object in e6uilibrium
'
… 1 …(…
-……………
2. ………………………………………………………………………………………………
normal reaction%
friction force
eight%
Force % F ( Frictional force
t G s t G s
-
8/17/2019 Chapter 2 Force and Motion (Answer)
34/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
esultant force ( F 1 Frictional force( - &object 2in2 e6uilibrium'
-
8/17/2019 Chapter 2 Force and Motion (Answer)
35/108
2!
stationary obIect
6n obIect moin" with uniform elocity
Addition o! Forcea resultant force is a single force the
1. 6ddition of force is defined as ...……………………………………………………..represents in magnitude and direction t3o or more forces acting on an object ……………………………………………………………………………………………… F resultant ( the total of forces &including the directions of the forces'………………………………………………………………………………………………
L9amples : the forces are acting in one direction
;1 10 G
;2 G
=esultant force+ ; ( F . F 2 ( - . * ( * N
L9ample : the forces are acting in opposite directions
;1 10 G
;2 G
=esultant force+ ; ( F # F 2 ( - # * ( * N
L9ample : the forces are acting in different directions
;2 G
-
8/17/2019 Chapter 2 Force and Motion (Answer)
36/108
00 ;
Barallelo"ram method:
1. raw to scale.
2. raw the line parallel with ;1 to the ed"e of ;2+ and the line parallel with ;2 to the
ed"e of ;1
!. ,onnect the dia"onal of the parallelo"ram startin" from the initial point.
#. Eeasure the len"th of the dia"onal from the initial point as the alue of the
resultant force.
Trian"le method
+olution : esultant force% F ( 5--- 1 *$--1. raw to scale. (/-- N
2. isplace one of )h
thee y
f 3
oerc
rees
ntoo
ttihneee6
du"il
eib
or f iu
am
nother force.
!. ,omplete the trian"le and measure the resultant force from the initial
point.
$%ample 1: urin" Sport ay two teams in tu" of war competition pull with forces of
/000 G and !00 G respectiely. Hhat is the alue of the resultant forceF
6re the two team in equilibriumF
esultant force% F ( -!* 9 *-
( *2* N
;1 10 G
;2
;
;1
-
8/17/2019 Chapter 2 Force and Motion (Answer)
37/108
600
F
θ
F 9
re
$%ample 2: 6 boat in a rier is pulled horiJontally by two wor-men. Hor-men 6
pulls with a force of 200 G while wor-men while wor-men ' pulls with a
force of !00 G. The ropes use+ d ma-e an an"le 20 with each other.
raw aCos θ ( % therefore F 9 ( F cos θ
parallelo"ram and label the re+ sultant force usin" scale of 1 cm : 0 G.
etermine the ma"n+ iitnudθe(of +
y su %ltt ahnetrefo forcree. F ( F sin θ+
F 9 ( F cos θ ( *- cos 5-
( *- &-!*'
( 2* N
Resol$tion o! a !orce
Fy ( F +in θ ( *- sin 5--
F y ( *- &-!;55-'( 4$!$ N
re"erse process of finding the resultant force1. =esolution of a force is …………………………………………………………………
F y F is the resultant force of F9 and Fy )herefore% F can be resol"ed
into F9 F an(d m F g y sin 4-- . 2--( ;--&-!542/' . 2--
Dertical
Component
( *4!2 . 2--
( /4!2 N
hori8ontal component
mg ( ;-- N
=efer to tri"onometric formula:
$%ample : The fi"ure below shows 6li moppin" the floor with a force 0 Gat an an"le of /00 to the floor.
; 0 G
20
10. cm F 9
-
8/17/2019 Chapter 2 Force and Motion (Answer)
38/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
$%ample of resolution and combination of forcesF = ?
*ro1lem solvinthe resultant force is e6ual to 8ero!
1. Hhen a system is in equilibrium+ ……………………………………………………….
2. 7f all forces actin" at one point are resoled into horiJontal and erticalthe sum of each component is e6ual to 8ero!
components+ ……………………………………………………………………………
!. $%ample 19 Show on a fi"ure9
a) the direction of tension force+ T of strin" b) the resultant force act to lamp
700 700 c) calculate the ma"nitude of tension force+ Tma9imum 3hen both of forces act in same direction F a)T b) TK T &c ' )K ( 2) sin /-
-
F ma9imum ( ; . 5 ; N 24 N
( 24 N )herefore% mlamp g ( 2) sin/-- 5 N
F minimum 3hen thm
e l f aomprc
es1.
act
-"in
opposite direction
mlamp
& ) (
sin00
F minimum ( ; 1 5 Hlamp 1#.@ G
; N 2 N
E%ercise 2.?
( 2 N 5
N (
/.5.1 #
sin0
0
( /!;2 N
1. Two force with ma"nitude 1? G and / G act alon" a strai"ht line. Hith the aid ofdia"rams+ determine the ma%imun possible alue and the minimum possible alue of the
resultant force.
F ( esultant of Force
F 2 ( 22-2 . 2--2
F ( 2
-
8/17/2019 Chapter 2 Force and Motion (Answer)
39/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
2/
-
8/17/2019 Chapter 2 Force and Motion (Answer)
40/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
2. H=* is
1. Hor- is done+
2. 6 football is -ic-ed simultaneously by two players with force 220 G and 200 G
respectiely+ as shown in ;i"ure 2.3. ,alculate the ma"nitude of the resultant force.
200 G
-NDERSTANDIN) ;OR@3 ENER)( AND EFFICIENC(
;or hen a force that acts on an object mo"es the object through a……………………………………………………………………………..
distance in the direction of the force!………………………………………………………………………………………………
of a force and the distance tra"eled in the direction of product.…………………………………………………………………….
the force!………………………………………………………………………………………………
!. The formulae of wor-9 @O ( F@CL ,+PE0CLMLN) ( F % s
: 3ork in JouleGJ
F : force in Ne3tonGN
s : displacement in meterGm
#. $%ample 19
;orce+ ;
( Fs s
f% F ( 4- N and s ( 2
m 7ence% ( 4- 9 2
( ;- J
$%ample 29
2@
220 G
300
-
8/17/2019 Chapter 2 Force and Motion (Answer)
41/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
; /00 G
( F s
( 5-- 9 -!;( 4;- J
S 0.? m
) )
h
?0 G
/00
( Fs s m
( ;- cos 5-- &*'
( ;- &-!*' &*'
( 2-- J
$%ample !9
F ( $-
N ( !*
m ( F s ( F h
( $- &!*'
( 4*!- J
$%ample #9
Enery t is the potential to do 3ork!
1. $ner"y is .................................................................................................................created nor be destroyed!
potential energy% kinetic energy% electrical 2?
energy% sound energy% nuclear energy% heat and chemical energy!
-
8/17/2019 Chapter 2 Force and Motion (Answer)
42/108
23
2. $ner"y cannot be ....................................................................................................
!. $%ist in arious forms such as …………………...……………………………………
………………………………………………………………………………………………
#. $%ample of the ener"y transformation9
hen 3e are running up a staircase the 3ork done consists of energy change from………………………………………………………………………………………………Chemical Lnergy à Oinetic Lnergy à Potential Lnergy……………………………………………………………………………………………
…)he energy 6uantity consumed is e6ual to the 3ork done!
. ……………………………………………………………………………………………… f -- J of 3ork is done% it means -- J of energy is consumed!$%ample : …………………………………………………………………………………
……………
;or done and t"e c"ane in inetic enery
Force, F
s
energy of an object due to its motion!1. *inetic ener"y is …………………………………………………………………………
2. =efer to the fi"ure aboe+ork ( Fs
( mas
( m & > "2 '
)he formulae of Oinetic energy% Lk ( > m"2
!. $%ample 19 6 small car of mass 100 -" is moin" alon" a flat road.The resultant force on the car is 200 G.
a) Hhat is its -inetic ener"y of the car after moin" throu"h 10 mF
b) Hhat is its elocity after moin" throu"h 10 mF
+olution : ?i"en : m ( -- kg % F ( 2-- N
a! Oinetic energy% Lk ( Fs
( 2-- 9 -( 2--- J
b! Delocity% "à > m"2 ( 2---
" ( 5!$2 m s#
*hrou&h, v = u 2asu = 0
and, as = 3 v
-
8/17/2019 Chapter 2 Force and Motion (Answer)
43/108
JPN Pahang Physics Module Form 4
m
!0
Chapter 2 : Force and Motion
h 1.created or destroyed but can be changed from one form to
another form!energy of an object due to its position!
1. Araitational potential ener"y is………………………………………………………...&possessed by an object due to its position in a gra"itational field'
……………………………………… M …a9…im…um… P …ot …en…tia…l e…ne…rgy…………………………
…2. =efer to the fi"ure aboe9
Oinetic energy decrease ( Fs ( mg h 3here% F ( mg
+o% ?ra"itationa pl ot eennet r i g a yl %e L ne p r ( gymd g ehcrease
potential energy and kinetic energy!.
an
d $%ample9 7f m 10 -" ( - &-' !*
ncrease ( *-
J
increase
)herefore ork done ( *-J
*rinciple o! conservation o! enery 0nd% L p ( *- J Ma9imum kinetic energy
,arry out hands5on actiity 2.10 on pa"e !? of the practical boo-.
To show the p?riin"cein pl:eho(f c2o-nsme %ruat(ion- o % f g e(nethe rate of doing 3ork!
)herefore% po3er% P ( 3orkdon
e
timetaken
% so% P (
t
here% P : po3er in 3attG : 3ork in jouleGJ
t : time to do 3ork in secondsGs
!. $%ample in calculation : 6 coconut falls from a tree from a hei"ht of 20 m. Hhat is theelocity of coconut Iust before hittin" the earthF
;or done and ravitational potential enery
-
8/17/2019 Chapter 2 Force and Motion (Answer)
44/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
Devce!
mec"#e
*oer
1. Bower is …………………………………………………………………………………
2. 6 wei"htlifter lifts 1?0 -" of wei"hts from the floor to a hei"ht of 2 m aboe his head in
a time of 0.? s. Hhat is the power "enerated by the wei"htlifter durin" this timeF
" 3.? ms52) +olution : ?i"en : m ( ;- kg% h ( 2 m% t ( -!; s and g (
P ( (t
mght /10 × .1 × -
E!!iciency (0.1
( 4 4-
as the percentage of the energy input that is transformed into useful energy!1. efined……..…………………………………………………………………………….
2. ;ormulae of efficiency :
Lfficiency = se ful energy output
×100L Lnergy input
!. 6nalo"y of efficiency9un3anted energy
Lnergy input% L input Devce!
mec"#e
seful energy% L output
$ner"y transformation
+olution : ?i"en : m ( -!2 kg% s( -!4 m% t ( * s% L input ( -!; J
#. $%ample9(6a)n L eoluetpcutt r (ic=motor in a toy crane can lift a 0.12 -" wei"ht throu"h a
hei"ht of 0.# m in s. urin" this time+ the batteries supply 0.? & of ener"y to the motor. ,alculate
&a' The usefu L l oout f puot u(tp F ut 9o sf the motor.
&b' The efficiency of (th&-e!m2o 9tor -' 9 -!4
( -!4; J
&b' Lfficiency ( =
L =
output
Lfficiency L
input =
0.48
0.80
-
8/17/2019 Chapter 2 Force and Motion (Answer)
45/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion 9 100L
x 100% = /0L
-
8/17/2019 Chapter 2 Force and Motion (Answer)
46/108
,arry out hands5on actiity 2.11 on pa"e !3 of the practical boo- to measure the power.
E%ercise 2.&B
1. Hhat is the wor- done by a man when he pushes a bo% with a force of 30 G throu"h a
distance of 10 mF State the amount of ener"y transferred from the man to the force.
( F s )he energy transferred to the force ( (b) Hhat is his power if he completes this wor- in 20 sF
P (
t 2205
(250
( ;!;2
-
8/17/2019 Chapter 2 Force and Motion (Answer)
47/108
A**RECIATIN) T+E IM*ORTANCE OF MAIMISIN) T+E EFFICIENC( OF
DE8ICES
1. urin" the process of transformation the input ener"y to the useful output ener"y+……… some of energy transformed into un3anted forms of energy!
……………………………………………………………………………..
)he efficiency of energy con"erters is al3ays less than --Q!.……………………………………………………………………………………………..)he un3anted energy produced in the de"ice goes to 3aste!………………………………………………………………………………………………
$%ample of wastin" the ener"y9 Oinetic energy
………..…………………
7nput ene"y output
from the petrol ener"y
Lnergy loss due to Lnergy loss Lnergy loss Lnergy loss due to friction at
…………………… ……………. ……………… ……………………. friction in as heat as sound other parts in the..………………….. …………….. ………………….. …………………….
mo"ing parts engine..………………….. ……………. …………………. …………………….
#. The world we are liin" in face acute shorta"e of ener"y.
. 7t is ery important that a deice ma-es ……………………………………………the best possible use of the input energy!
……………………
;ays o! increasin t"e e!!iciency o! devices Lngine must be designed 3ith the capability to produce greater amount of
1. 4eat en"ines ……………………..………………………………………………………mechanical 3ork!………………………………………………………………………………………………
2. $lectrical deices. ...……………………………………………………………………... Light Fittings……………………………………………………………………………………………# replace filament light bulb 3ith fluorescent lamps 3hich ha"e higher efficiency!……………………………………………………………………………………………# use a lamp 3ith a reflector so that the illumination can be directed to specific areas……of the user!
……………………………………………………………………………………………… Air-conditioners.………………………………………………………………………………………………
# choose a model 3ith a high efficiency!………………………………………………………………………………………………# accommodate the po3er of air#conditioner and the si8e of the room………………………………………………………………………………………………# Lnsure that the room totally close so that the temperature in the room can be………………………………………………………………………………………………maintained!
………………………………………………………………………………………………
………………………………………………………………………………………………
2.
!.
-
8/17/2019 Chapter 2 Force and Motion (Answer)
48/108
1. $lasticity is
2. ;orces between atoms
Refrigerators………………………………………………………………………………………………# choose the capacity according to the si8e of the family!
………………………………………………………………………………………………# installed a3ay from source of heat and direct sunlight!
………………………………………………………………………………………………# the door must al3ays be shut tight!
………………………………………………………………………………………………
# more economical use a large capacity refrigerator!………………………………………………………………………………………………# use manual defrost consumption!
………………………………………………………………………………………………ashing !achines
………………………………………………………………………………………………# use a front loading as such more economical on 3ater and electricity
………………………………………………………………………………………………# front loading use less detergent as compared to a top loading machine!
………………………………………………………………………………………………
Operation o! electrical devices3hen they are in good operating
1. The electrical deices increase the efficiency………………………………….……condition!3ill increase the life span of de"ice!
2. Broper mana"ement ….....……………………………………………………………… L9ample : #the filter in an air#conditioner and fins of the cooling coil of a refrigerator
!. …………..………………………………………………………………………………must be periodically cleaned!
………………………………………………………………………………………………
-NDERSTANDIN) E'ASTICIT(
,arry out 4ands5on actiity 2.12 pa"e #0 of the practical boo-.the property of an object that enables it to return its original shape and
……………………………………………………………………………...dimensions after an applied e9ternal force is remo"ed!
………………………………………………………………………………………………)he property of elasticity is caused by the e9istence of forces of …………………………………………………………………..
repulsion and attraction bet3een molecules in the solid material!………………………………………………………………………………………………
!. ;orces between atoms in equilibrium condition
Force o$ re%'so#
Force o$ ())r(c)o#
Force o$ re%'so#
$%planation :
! )he atoms are separated by a distance called the e6uilibrium distance and "ibrate at ………………………………………………………………………………………………it position!
………………………………………………………………………………………………2! Force of repulsion ( Force of attraction
………………………………………………………………………………………………
#. ;orces between atoms in compression
compressie forcecompressie force
-
8/17/2019 Chapter 2 Force and Motion (Answer)
49/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
1. 4oo-eKs
-
8/17/2019 Chapter 2 Force and Motion (Answer)
50/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
QP
*
!
0 R + cm
-
8/17/2019 Chapter 2 Force and Motion (Answer)
51/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
k
F ( k9+pring obeying 7ookeKs Ea3 +pring not obeying 7ookeKs la3
&e9ceeded the elastic limit'
Force constant% k ( F 3ith unit N m# % N cm# or N mm# 9
5! Sprin" ,onstant+ -
;>G
0.?
0 ? %>cm
k is the gradient of the F # 9 graph
F (
90.1 1
( -! N cm#
$%ample 19 6 sprin" has an ori"inal len"th of 1 cm. Hith a load of mass 200 "
attached+ the len"th of the sprin" is e%tend to 20 cm.
a. ,alculate the sprin" constant. b. Hhat is the len"th of the sprin" when the load is in increased
by 10 "F Massume that g 10 G -"51N
?i"en : l o ( * cm% m ( 2-- g % F ( 2!- N% l ( 2- cm 9 ( * cma. k ( =% k ( x = 2.0 = 0.4Ncm 1
F −
5
b. l ( = % 3hen m ( *- g% F ( !* N From a% k ( -!4 N cm#
9 (+=
.5= ?.@cm
k 0.4
$%ample 29l ( * . ;!/* ( 2$!/* cm
The "raph shows the relationship between the
Araph ; a"ainst % of stretchin" force+ ; and the sprin" e%tension+ %.
F N
.
7
6/
sprin" B and sprin" C
P
Q
(a) ,alculate the sprin" constant of B and C.(b) 8sin" the "raph+ determine the
stretchin" force acts to sprin" B
and
sprin" C+ when their e%tension are 0. cm
+olution
a! +pring constant% k ( gradient of graph6 −k P (
40.3
8
=15.79N cm1
k B (2
3= 6.0 N cm
−
10.5
(
-
8/17/2019 Chapter 2 Force and Motion (Answer)
52/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion1
0 0.1 0.2 0.! 0.# 0.% (cm)
b! hen 9 ( -!*% F P ( ;!- N & e9trapolation of graph P'
F B ( $!- N
-
8/17/2019 Chapter 2 Force and Motion (Answer)
53/108
!@
%
Elastic potential enerythe energy stored in a spring 3hen it is e9tended or compressed
1. $lastic potential ener"y ………………………………………………………………..
sprin" with the ori"inal len"th
% sprin" compressed %
; % compression
% ; sprin" e%tended
; compression
% e%tension;+ e%tension
ther situation where the sprin" e%tended
and compressed
Relations"ip 1eteen or and elastic potential enery
F!N
F
Araph ; a"ainst %
+
0rea under the graph ( 3ork done
( > F9+o% Llastic potential energy ( > F9
$%ample 9
1/ cm
+ ! cm
/ g
. cm
9 ( * 1 ;
( / cm( -!-/ m
Force act to the spring%
F ( * 9 - ( *- N Llastic potential energy ( > F9
( > *- &-!-/' ( !/* J
Factors t"at e!!ect elasticity
4ands5on actiity 2.1! on pa"e #2 the practical boo- to inesti"ate the factors that affect
elasticity.
-
8/17/2019 Chapter 2 Force and Motion (Answer)
54/108
Type of material different same same same
iameter of sprin" wire same different same same
iameter of sprin" same same different same
$estions
1 Hhen a coconut is fallin" to the"round+ which of the followin"
quantities is constantF
-
8/17/2019 Chapter 2 Force and Motion (Answer)
55/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
Solution :
6. Velocity
'. Eomentum
#. Acce$eration
. *inetic ener"y
2 7n an inelastic collision+ which of thefollowin" quantities remainsconstant before and after the
collisionF
6. Total acceleration
Velocity > ms51
#
0 2 # / Time > s
,alculate the momentum of the
trolley from t 2s to t #s.
'. Total elocity
#. Tota$ !o!ent%!
. Total -inetic ener"y
,alculate the wei"ht of a stone withmass /0 " on the surface of the
moon.
6. 1. -" m s51
'. !.0 -" m s51
,. #.0 -" m s51
&. '.( )g ! s-
1
$. @. -" m s
51
P ( m"
( !* 9 4
( 5!- kg ms#
(The "raitational acceleration of the @. This fi"ure shows an aircraft flyin"moon is 1>/ that of the $arth.)
in the air. m"
2
&-!$'&-'&*' ( > &-!$' "2
" ( - m s#
P ( &-!$'&-'( $!- kg m s#
m 0.! -"
m
-
8/17/2019 Chapter 2 Force and Motion (Answer)
56/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
Method &a'
)he forces gi"en parallel 3ith the surface of motion%
#2
3. 6 bi" ship will -eep moin" for somedistance when its en"ine is turned off.
10. 6n iron ball is dropped at a hei"ht of
10 m from the surface of the moon.
,alculate the time needed for theiron ball to land.
(Araitational acceleration of the
moon is 1>/ that of the $arth and" 3.? G -"52)
s ( ut . > gt 2
( &-'t . > &
ia"ram 1.1
ia"ram 1.1(i) and (ii) show two methods used by the mechanic to moe a brea-downcar. 6 constant force+ ; 00 G is used to push and pull the car in method 6 and '.
(a) (i) F H(hi F c g hi"emn #et F h f oricdtioins easier to moe the carF
…(…*-…- … 1 2…
--…………………………………………………………………
(ii) S(tat$e-a- r N eason for your answer in (a)(i).
……………………………………………………………………………… F ( F gi"en Cos *-
- 1 F friction
………………………………………………………………………………( *-- cos 5-- 1 2--
(b) The frictional force actin" between the car and trac- surface in both methods is
200 G. ,a(lc*u-la!-te N + the(i) horiJontal resultant force in method 6.
F ( m a
*-!- ( --- a(ii) horiJontal resultant force in method '.
a ( -!-* m s
)he acceleration of Car 0 ( -!$ m s#2
)o mo"e Car 3ith the same acce#l 0eration of Car 0% increase the force gi"en
This situation happens because the ship 6 0./ shas ' 1.# s
, 1.@ s
A. great inertia & . s
'. "reat acceleration $ 12.0 s,. "reat momentum
. "reat -inetic ener"y
-
8/17/2019 Chapter 2 Force and Motion (Answer)
57/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
to --- N
-
8/17/2019 Chapter 2 Force and Motion (Answer)
58/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
#1
(iii) acceleration of the car in method '.
( c ) Su""est a method to moe ,ar ' so that the acceleration produced is equal to thatof method 6.
……………………………………………………………………………..………..
………………………………………………………………………………………
2. ceilin"
Tin water E G hand
B C =
(i) ia"ram 2.1 (ii)
a) ia"ram 2.1(i) shows tin B that is empty and tin C that is filled with water. 6
student find difficult to pushed tin C. Hrite the inference about the obseration.)he difficulty to mo"e the tin depends to its mass!………………………………………………………………………………………
b) ia"ram 2.1(ii) shows a tin bein" released from the different positions E and G.
The hand of a student at position = needs "reater force to stop the motion of thetin fallin" from position E. $%plain this obseration.
From position M the "elocity of tin is more than the "elocity compare 3hen it is………………………………………………………………………………………
from N! L k increase then the force to stop it 3ill be increased!………………………………………………………………………………………
c) 'ased on the obseration (i) and (ii)+ state two factors that affect the ma"nitude of
the momentum of the obIect.
mass and "elocity………………………………………………………………………………………
d) 7f water flows out from a hole at the bottom of the tin C+ how would the inertia of Tin C depends on time F
inertia of tin B 3ill decrease because the mass of tin decreased!……………………………………………………………………………………
!. 2 ms51
-
8/17/2019 Chapter 2 Force and Motion (Answer)
59/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
-
8/17/2019 Chapter 2 Force and Motion (Answer)
60/108
JPN Pahang Physics Module Form 4
Chapter 2 : Force and Motion
B iron ball ( 2 -" )
!.0 m smooth surfaceS T
1.0 m 2.0 m
C = ia"ram ! =ou"h surface
The fi"ure shows a iron ball that is rolled throu"h BC=ST. The rou"h surface of C= has
frictional force of # G.a) ,alculate
(i) the -inetic ener"y of the iron ball at B.
L k ( > m"2
( > &2'&22 ' ( 4!- J
(ii) the potential ener"y of the iron ball at B. L p ( mgh
( &2' &-' &$!-'
( 5-!- J
(iii) the total of ener"y of the iron ball at B. L ( L k . L p
( 4!- . 5-!-
b) ( 54!- J
c) (i) ,alculate the total of ener"y of the iron ball when it reaches at C F54!- J & the conser"ation of energy '
(ii) ,alculate the wor- done a"ainst friction alon" C=. ( F f 9 s
( 4 9 !-
( 4!- J
d) ,alculate the total -inetic ener"y of the iron ball at S. L s ( L 1 L f L k at + ( L s # L p at s
( 54!- 1 4!- ( 5-!- 1 &2'&-'&2!-'
( 5-!- J ( 2-!- J
e) ,alculate the speed of the ball at position T.
L k at ) ( 2-!- J "2 ( 2-
( > m "2 " ( 4!* m s#
( > &2'&"2 '
*art C / Essay >$estions
1.
#2
-
8/17/2019 Chapter 2 Force and Motion (Answer)
61/108
#!
(i) (ii)
ia"ram 1.1
ia"ram 1.1(i) shows the condition of a car moin" at hi"h elocity when it suddenly
crashes into a wall.ia"ram 1.1(ii) shows a tennis ball hit with racquet by a player.
a) (i) Hhat is the meanin" of momentumF
(ii) 'ased on the obserations of ia"ram (i) and (ii)+ compare the
characteristics of car when it crashes into the wall and the tennis ball when
it is hit with a racquet. 4ence+ relate these characteristics to clarify a
physics concept+ and name this concept. b) $%plain why a tennis player uses a taut racquet when playin".
c) 7n launchin" a roc-et+ a few technical problems hae to be oercome before theroc-et can moe upri"ht to the s-y. 'y usin" appropriate physics concepts+
describe the desi"n of a roc-et and the launch techniques that can launch the
roc-et upri"ht.
0ns3e
r a' &i' momentum is product of mass and "elocity
&ii' # )he shape of car changed but the shape of 3all remained!# )he shape of ball remained but the shape of the rac6uet string 3as
changed! &)he rac6uet string is elastic but the 3all is harder'# )he time taken of collision bet3een the ball and rac6uet string
more than
the time taken 3hen the car hit the 3all!# )he impulsi"e force 3ill decrease 3hen the time of collision increased!
# )he concept is the impulsi"e force!
b' # )o decrease the time of collision bet3een the ball and the rac6uet string!
# mpulsi"e force 3ill be increased!
# )he force act to the ball 3ill be increased!# )he "elocity of ball 3ill be increased!
c' # Make a gradually narro3er at the front shape &tapering'
: )o decrease air friction# Made by the high strength and high rigidity of materials
: )o decrease the probability to become dented &kemik'!
# Made by the lo3 density of material!
-
8/17/2019 Chapter 2 Force and Motion (Answer)
62/108
: )o reduce the massG3eight
# )he structure is fractional engine
: )he mass 3ill be decreased and the "elocity 3ill increase!# Made by the high of heat capacity of materials
: t 3ill be high heat resistance!
2.Broperties
'rand =eaction time > s Eass > -"$n"ine thrust
force > G=esistance force
> G
6 0.! 1. 10.0 #.0
' 0. 1.? 12. 2.#
, 0.2 0.3 /. 2.2
0./ 2. 1/.0 /.
7n a radio5controlled car racin" competition+ # mini5cars branded 6+ '+ , and too- part.
The information of the # cars is "ien in the table aboe. etails of the aboe information
are "ien as below9
=eaction time 5 uration between the moment the radio5controlled is switched on and
the moment the car starts moin".=esistance 5 6era"e alue of opposin" forces includes the friction between
wheels and trac-+ and air resistance.
(a) Hhat is the meanin" of accelerationF
(b) raw a "raph of elocity a"ainst time that shows a car moin" initially with
constant acceleration+ then moin" with constant elocity and followed byconstant deceleration until it stops.
(c) $%plain the suitability of the properties in the aboe table in constructin" a radio5
controlled car racin" purpose. 4ence+ determine which brand of car will win the05metre race.
(c) 7f ,ar ' in the aboe table is moed up the plane at the an"le of !0o to thehoriJon+
(i) Show that the car is able to moe up the plane.
(ii) etermine the acceleration of the car. 0ns3er :
-
8/17/2019 Chapter 2 Force and Motion (Answer)
63/108
&a' ncrease the "elocity
&b' " G ms#
displacement ( area under the graph
t G s
&c' # time reaction mast be short : fast to detect the signal to start its mo"e# has a small of mass : to decrease the inertia% then easier to start mo"e and
to stop its mo"ing!
# thrust force is high : has more po3er during its mo"ing G increase the
acceleration# friction force is lo3 : decrease the lost of force
# the best car is 0 : because it has short of time reaction% small of mass% high of
thrust force and lo3 friction of force!&d' &i' L ( &2!* 1 2!4 ' &*-' ( *-*!- J
*- m *-+in$-- L &suitable to mo"e up' ( !;
&-'
&*-+in$-
-
'
!00
( 4*- !- J L L & car can mo"e up the plane'
&ii' F ( ma % 2!* 1 2!4 ( !; a% a ( *!5 ms#
-
8/17/2019 Chapter 2 Force and Motion (Answer)
64/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
65/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
66/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
67/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
68/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
69/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
70/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
71/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
72/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
73/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
74/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
75/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
76/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
77/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
78/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
79/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
80/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
81/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
82/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
83/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
84/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
85/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
86/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
87/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
88/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
89/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
90/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
91/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
92/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
93/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
94/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
95/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
96/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
97/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
98/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
99/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
100/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
101/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
102/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
103/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
104/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
105/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
106/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
107/108
-
8/17/2019 Chapter 2 Force and Motion (Answer)
108/108
!/