Forces and Mot

@."f-p,g:,*.:*.9-"9j?.""ti*,9y,,"**glllnstruction: Answer all questions. Each question is followed by either three, tour, or live options.

Choose the best optian for each question.

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Aclam rides a mototcycle. Bernard runs andChandra cycles. Table 1 shows the distancetravelled and the time taken by these threestudents.

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Adam 30 km t hourBernard 100 m 15 s

Chandra 24Okm 10 hours

Table 1

Which statement showsthe correct comparisonof their speeds?A Adam's speed is the same as Bernard's

speed.B Ghandra's speed is greater than Bernard's

speed.C Adam's speed and Chancjra's speed are

greater than Bernard's sPeed'D Bernard's speed is the same as Chandra's

but it is less than Adam's sPeed'

Sitoh travels from town P to town S as shownin Figure 1.

o

5kmR

2kmFigure 1

What is the displacement of Sitoh?

ii.r.?tliiif i* 4cn-i

Figure 2 D rlf the frequency of the ticker timer is 50 Hz,find the acceleration of the object.A 750 cm s-2 C 1250 cm s+B 1000 cm s+ D 1750 cm s-2

4 A stone is released from a height, h. lt takes2.0 s to reach the ground. The height, h is l*.ktlttA 8mtt tum

C 15mD 2Om5

.#lt.r,93'

Figure 2 shows a graph of acceleration, aagainst time, f of a moving vehicle.

a/m s-2

Figure 3

Which graph of velocity, t against time, fshows the motion of the vehicle?

2a$iir.:ala''lgPt

A 5kmB 12km

C 13kmD 21km

8 Figure 5 shows a velocity-time graph for the

Which of the following describes the motionof the object?

U,J

A Uniformacceleration

B lncreasingacceleration

C lncreasingacceleration

D Uniformacceleration

.KLDecreasingaccelerationDecreasingaccelerationUniformaccelerationUniformdeceleration

An object stafts from rest and moves withconstant acceleration. Which graph represents

Ef Llnderstanding Inertia iWhich device can be used to actually measutthe mass of an object?A Beam balanceB lneftia balanceC Spring balanceAn experiment is carried out using aapparatus as shown in Figure 6.

Figure 6

A student uses the apparatus to compare tlmass of two different objects by determinirtheA amplitude of the vibrations of the jigsa

blade.B period of vibrations of the jigsa

blade.C length of the jigsaw blade.D axis of vibrations of the jigsaw blade.Headrest is one of the safety features in a cto prevent neck injury due toA momentum.B inertia.C force.D pressure.

10

11

c

12

Figure 5

the motion of the object?

After collision1-SolleyA + B) i

20 Figure 12 shows a strip of ticker-tape beforeand after the collision of trolleys 4 and 8.Trolley I is stationary before the collision.Trolleys A and B are stuck and move in onedirection after collision.

Figure 12

lf the mass of trolley B is '10 kg, find the massof trolley,4.A 10kgB 15kg

21 The displacement-time graphs below showthe motion of an object. Which graph showsa resultant force acting on the object?As

rlI exn | 4ms-1 ts-G

F=8N

r-1I ,nn | 4msa

'LTGF=8N

?(ffi

B ;tltracre!

,. :lgili N:t :leA1ig 2',

*** SlAKgBN

G>i-: I t

fe imA 6.{I 1.:-3UKlee ro3ll"tef i

c

D

?ffi

C 2okgD 22kg ffif\E

&...

23 When 3 kg massan accelerationFigure 13.

is released, it moves withof 2 m s-2 as shown in

A 12N e 24NB 18N D 36N

Ec24

Figure 13

Caleulate the tension of the string.[Useg=10ms-2].

A block of mass 0.5 kg is pulled by a force of20 N as shown in Figure 14. The bloek moveswith a constant velocity on a rough surface.

Figurc 14

Find the frictional force betweenand the surface.A 15NB 18Nc 20ND 3ON

the block2, Which of the following figures state the correct

value of resultant force, Facting on the objectof mass 2 kg?A

2 k;--]___4N 1ONF=14N &

Underfranding the F=20N

Safetg Features in l

tT

32 Which feature below does not describe thedesign of a seat belt?A The length of the seai belt is adjustable.B The seat belt must nof be easily stretched

during the collisionC The width of the seat belt is widen.Which of the following statements explainscorrectly the function of certain safety featuresin a vehicle?A The air bags inflate on collision to reduce

the force of side impacts.B The passenger seat must'be strong

enough to protect the passenger fromhitting the steering wheel.Dashboard is made of laminated glassto prevent sharp edges on collision.The headrest is installed to protectthe passengers when the vehicle is hitfrom behind.

36 An astronaut jumps from the spacecraft ata height ol 2 m above the surface of theMoon. lf the gravitational acceleration of the

1Moon is U of the Earth's gravitationalacceleration, calculate the time taken by theastronaut to reach the surface of the Moon.A 1.5 sB 2.4s

A 72ONB 1280 N

C 3.2sD 4.9s

F {ArrN NIv tuvu ttD 1920 N

{t,t I

rtat37 Figure 21 shows a man of mass 60 kg in

a lift ascending with an acceleration of2.0 m s-2.

Figure 21

lf the mass of the lift is 100 kg, find thetension in the cable.

UitA

uffir?.-qPr

@ lJnderrtanding Eravitg j"iFigure 20 shows two coconuts of differentmass falling from the same height and hitthe ground.

Figure 20

What is the same physics quantity for bothcoconuts?A Gravitational poiential energyB Time taken to hit the groundC Kinetic energyD MomentumA free fall isA falling due to gravitational attraction.B falling without being acted by an external

force.C falling across the air resistance.D falling with zero- acceleration.

EEf Analg-sing Forces in

38 An object is acted by two forces, X andY perpendicularly to each other with themagnitude of 8 N and 10 N respectively.Find the magnitude and direction of resultaniforce on the object.A 6.0 N at 38.7" with force X.B 12.8 N at 51.3" with force X.C 18.0 N at 51.3" with force Y.D 36.0 N at 38.7" with force Y.

39 Figure 22 shows an object Q with mass 2 kgacted by a force of 10 N at an angle of 60"on a smooth inclined Plane.

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_-il

35

;

4Figure22

AryB ts?t9

A mg(, cos 0vtD (mg!. sin 9lt

50 Figun.nn

J,V

:, thrshowciaceirgun---]-_

,/'i!c)ol:z,

A W andXB XandYC XandZD YandZ

Understanding Elasticitg

(c) The object moves with a constant acceleration. What is the acceleration of object P?

[2.'marks]

2 A gardener pushes a lawnmower on a grass field. He applies a force of 300 N pushing the machineat an angle of 30' as shown in Figure 2. The mass of the lawnmower is 120 kg.

Figure 2

(a) Find the force that causes the lawnmower to move forward.

12 marksj

(b) Find the total force that acts vertically downwards whilst the lawnmower is movingfonrvard.

13 marks';

(c) The effect of cutting the grass is less if the gardener pulls the lawnmower at an angle of30' along the field. Explain.

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I

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. ...,1a.i:1

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ii' irtl'it;rj

l,;ii:'i'ti:ii

13 mark{

markl *.lir

(a)

(b)

Draw the arrows on Figure 4 to show the direction of the forces acting on point Pi1

(i) Draw a vector diagram to represent the parcel in a state of equilibrium.Figurposii

[2 marks](iD What is meant by the parcel in a state of equilibrium?

11 markJ

(c) Find the tension in strings Y and Z.

[3 marks]

(d) Describe what will happen to string Y and string Z if each of the strings can withstand amaximum force of 40 N.

[2. marks]

(e) lf string X breaks suddenly, find the time taken by the parcel to reach the surface of theground.

[3 markil

a3:

ill1F lJnderstanding Work, Energg, Pow,pr and Efficienrg e6 Figure 6 shows a woman lifting a pail of water of mass 5 kg from a well using a pulley system.

She applies force of 60 N to pull the rope down '1.5 m. The pail of water is raised to a height of1.5 m from the well.

(a) What is meant by work?

7AnUdLina

Figure 6

(b) Calculate the work done(i) by the woman to pull the rope down a distance of 1.5 m.

(iD on the pail of water to raise it to a height of 1.5 m.

(c) State why there is a difference between the work done in 6(b)(i) and 6(bXiD.

11 markl

12 marksj

12 marksj

[1 markl

ffi8 A spring with original length 4O cm is used to support object A and object B respectively as

shown in Figure 8.

40 cmI

I(a)

Figure 8

(a) State Hooke's law.

11 marl4

(b) (i) Based on Figure 8, the mass of object A is 4 kg. What is the mass of object B?

[2 marksj(ii) State one assumption made to explain the ansrlrer in 8(bXi),

tttlttitTLIF".Frlol)otrg

(b)

rC; Thpot,)

tx&luction

8:

(il/

6A Pry

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"l ffil

(c) Calculate the elastic potential energy stored in the spring in Figure 8(c).11 marKl

12 marks'i

Define momentum. 11 marl

(a)

(b)

(i) At which region of the graph, the skier crouches his body into an 'egg position'?11 markJ(ii) Explain your answer in 11(a)(i). [2 marks]

0 Calculate the acceleration of the skier at SU. [2 marhsj

Figure 11.3[3 marksj

(c) Suggest one way in which the skier can reduce his speed while reaching the bottom of thehill. Explain your answer. [2 marksj

(d) You are representing the school to bring a group of 35 students for a competition in Kedah.Table 11 shows the characteristics of four types of school bus.

td rryffiuctior

(i0 Sketch a graph of acceleration against time for the motion of the skier at S, U, V and EEFW in Figure 11.3.: - r-

Acceleration/m s-2 :je'e

.-,4;(

/

' ,l--{--.\

';rrg2'1-

:-aBased on Table 11,(i) explain the suitable characteristics of the school

safety and the comfort of the students.(ii) determine which model of school bus is mostchoice.

bus so that it helps to improve the

suitable to be chosen. Explain your110 marksj

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11 ri :,i:iJ,!j

Table 11

(iii) Catculate the frequency of the oscillations when 3 metal rods are set to oscillate. One t

(c)

13 marksl

of oscillation of metal rodsWhat wili happen to the period of osciliations when the speedincreases?

11 markl

(d) state two precautions that should be taken during this experiment.1.

2.

[2 marks]

H.:"o"r*""o,"g *" 8 *2 A student carries out an experiment to study the relationship between the acceleration and the

mass of an object. Figure 2.1 shows the arrangement of the apparatus in the experiment.

Ticker tape

12V a.c.Power suPPlY

Figure z'1

At the beginning of the experiment, a trolley is used. The trolley is pulled down the plane bystretchinglhe elastic cord to the end of the trolley. The frequency of the ticker timer is 50 Hz.The experiment is repeated by using two trolleys and three trolleys. The ticker tape obtainedeach time is cut into strips of s-tick and the ticker tape charts for the motion of the trolley areconstructed as shown in Figures 2.2,2.3 and 2-4-

,,tO tf

Ticker timer

(a) Based on the aim and the procedure of the experiment, identify:(i) The manipulated variable

11 mark(ii) The responding variable

[1 mark(iii) The constant variable

[1 mark(b) Measure the lengths of the ticker tape and calculate the initial velocity, final velocity and

acceleration where n =Y.

16 marks

Tabulate your results for number of trolleys, m, ) and acceleration.

Plot a graph of acceleration n against I on tne graph paper on page 47.'mBased on your graph, state the relationship between a and m.

[3 marks

[3 marl*(c)

(d)

11 mart

lfi4.

@,,ryr:*|, : s."tl-on Plnstruction: Answer all questions.

3 Figure 3 shows "

rotterl""t"r. -

Figure 3

When the roller coaster slides down from a higher levei, its speed before reaching the lower leveincreases. Using this information:(a) Make one suitable inference. [1 mar\(b) State one appropriate hypothesis that could be investigated. l1 mark(c) Describe how you can design an experiment to test your hypothesis using ticker timer anc

other apparatus. ln your description, state clearly the following:(i) The aim of the experiment.(ii) The variables in the experiment.(iii) The list of apparatus and materials.(iv) The arrangement of the apparatus.(v) Thq procedure of the experiment, which includes the method of controlling the manipulatec

variable and the method of measuring the responding variable.(vi) The ways you tabulate the data.(vii)The ways you analyse the data.

rdfllb.*tn

i'{*'-{ nui'

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NFW.

[10 marks

,! =;-: ':.

A student carried out threedifferent experiments bysimply pulling a ticker tapethrough a ticker-timer. Frolnsome,rvhere about the middleof the tape, he cut off 5pieces of each l0-tick strip.He then pasted them side byside as shown in the diagramsbelow. Which diagram showsconstant acceleration?AB

1.20 crn

DIAGRAM4If the ticker-timer has atiequency of 50 Hz what is theacceleration of the trolley?A 5.0 m s-r C 15 m s.'2B l0msr D 20ms-r

12 Diagram 5 is a velociry-time"*Ptt craoh of an obiect.:zoo, I "v v"'locity

Time

DIAGRAM 5Which of the foliowing bestdescribes the motion of theobject?

10

:1*r*i"

a?I

I

I

I

I

.rn ofough

s the

stallt

iti-t nt

d

crfrirePL'r

C L"ngth/crnAlr

tll.l tll'liliH:l ,u Timeis

11 Diagram 4 shorvs a section of,gPat the ticker taoe obtained when'

,rce

ljectving

nof

the

" the

'the

with.rghtlrcethe

What is the accelelation of thebox?A 5.0 rn s'2 C 15.0 m s-:B 10.0ms-: D 50.0ms:

30 A truck of nass 5 000 kg is,5prh. moving rvith an acceleration is'4!!]"t t.5 m s :. If the total fiictional

force on the truck is 4 500 N.rvhat is the force exerted bythe truck's engine?A 45500NB t2 000Nc 7500ND 3000N

lmpulse andlmpulsive Force

31 Diagram 16 shows threeidentical lurnps of plasticinefall from the sarne heightonto three dillbrent types ofhorizontal surfaces.

DIAGRAM 16All the lumps do not bounce onirnpact. The impulse impartedto the surfaces by the luntps isA least lbr rvoodB greatest fbr ironC the same for all surf'accsDiagram l7 is a graph whichsholi,s how the fbrce, F.changes with tirrre. t. tvlienacting on an object.

F/N

impulse equal toA 5Ns C 20rr"B 15Ns D 30N

to an

S

s

A car of mass 2 000 kgtravelling. at a vclocity of20 m s'r crashed onto a lamppost and was brought to a stopin 5.0 s. What is the magnitudeof the impulsive force on thecar?A 8000N c 20000NB 10000N D 40000N

34 A ball of nrass 5.0 kg strikesa wall with a velocity of5.0 m s-r. It bounces backwith a velocity of 3.0 rn s-r. Ifthc ball is in contact with thervall for a time of 0. I 0 s, whatis the average force acting onthe rvall by the ball?A I5ON C 3OONB 25ON D 4OON

i33I

I

i

l

the)nalgather

iL^tllt

COOIJJ

i 35 Diagram 18 shows a gymnast,

"$Prt. bending her legs u hile"Wt landinj after performing oni the balance beam.

ofrn.Y

u illr ith

DIAGRAIT 18This ulotion is necessaryA to quicken her landingB to keep the impulsive

lbrce constantC lbr an increase in the

distance used for landingD to delay tirne of impact

rvith lhe ground

I 36 Anairplaneonarescuemissronrrrlr drops a 75 kg lood pack. Just

' ;{9k 6q1br.' it striies the ground it

rvas travel ling vertically downrvith a velocity of 12 m s-r. Onstriking the ground. it rvasbrought t0 a stop in 1.2 s. Themagnitude of the impulsiveforce on the food pack isA 625N C 900NB 750N D 3000N

32

ina

Concrctc Wood

2{{iDIAGRA}I I7

The object is sub-iected

15

37

Safety Features inVehicles

For the safety of a toddleqnever have the toddler seatedin the tiont passenger seaifacing the back ofthe car. Thisis toA avoid ltaving his facc

thrown to the back andbreak his neck

B enable the driver tomaintain eye contact withthe toddler

C avoid the toddler piayingwith his toys rvithoutsupervison

Assuming the car's speed isconstant. all of the fbllowinghappen to a vehicle when it isover loaded exceptA its inertia is increasedB its momentum is increasedC the disiance nceded to stop

is increasedD the car is more stable and

can travel faster

so?A To increase the

timeB To increase

rmpact

them()mentum

C To decrease the irnpulseD To decrease the friction

38

39 The front and rear sections of,lgtv,a car are desicned to crumplerioJll sss;1y on inrpact. Why is this

@ Gravity40 An apple of 50 g mass hanging

by a tree branch suddenly fallsto the ground. Joe Hong picksit up and places it on a table.In each ofthe three situations.the gravitational force actingon the apple isA greatest rvhen resting on

the tableB greatest rvhen it is fallingC same in all situations

gfamnship', and

51 When forces acting on anosnh, object arc in equilibrium. the-200r, ..r".r ObJeCt mUSt

A be stationaryB be moving with constant

velocityC be either stationary or

moving ivith constantvelocify

D be either moving withconstant acceleration orconstant velocity

Work, Energyn Powerand Efficiency

A box of 5 kg mass is draggedacross a smooth floor usinga rope rvhich makes an angleof 60o to the horizontal asshorvn in Diagram 26. Thetension in the rope is 200 Nwhile the box is being draggedl5 m.

DIAGRANI26How much rvork is done?fAssuming there is no frictionrorincf fl.p h^-l

A 2600J C 7501B 1500i D 375JA hammer used in thedenrolishing of a tall buildinghas a mass of 30 kg. It is tiedto a 5.0 m long rope. It swingsfrom rest at position X andthlls to position Y, as shorvnin Diagrarn 27.

DIAGRANI2TWhat is the speed of thehamrncr on reachinq positionY?

A 3.2msr C 30rns'B 10fils'r D 50ms-r

54 A lift in an apartment can carry8 residents through a height of9 m in 6 s. The total mass ofthe lift and the residents is 900kg. If the porver input of thelift motor is 20 kW" what is theefficiency of the motor used inthe lift? [g: I0 m s"']A 100% c 40.5%B 67.5% D 6.8%

57 Diagram 30 shows a crane.seth., lifts a heavy bucket of750 kgqP

mars to a t eigrrt of 3.5 m fromthe ground in 4.5 s.

Calculate the rvork done inlifting the bucket. [g : l0 m s-2]A 21401 C 262501B 5830J D 33750J

The lmportanceof Maximising theEfflciency of Devices

An increase in elficiency of amotor rvould meanA an increase in power

outputB an increase in operational

costC an increase in wastage of

energyD an increase in fuel

consunrption

A poorly maintained car wasfound to rattle and overheatafterjust a shoft distance. Theenergy is lost in the fonns ofA lieat and lightB heat and soundC sound and light

{,)r.

)l'r

:S, F,odenface.rlockN.

=r,* Table

surfacc

ruses

nove

52

55 Diagrarn 28 shows a motor,2!g,lifting a load of 80 kg massf3391u"6;s;lly up to the roof top of

a 50 m tall building.

58

rtrngtwo

53tnt

.:!

Iram,tr.. l.

DIAGRAM 28If thc rnotor takcs 50 s toaccomplish the job, rvhat isthe power of the motor?

i A t000w c l00wB 800w D 80w

I 56 Diagram 29 shows a monkey,rr.,rr climbing up a coconut tree at'lJF aconstant speed.

What physical quantityincreases rvhile the rnonkey isclinrbing up the coconut tree?A Potcntial energy of the

monkeyB Kinctic cncrgy of the

monkeyC Momentum of the

rnonkc5+ -

D Inerlia of the monkeJ_

:t, 59i

I

i60ii

C l75gD l00g

DIAGRAM 30

DIAGRAM 29

@ Etasticity

ler

A mass of 100 g attached tothe end of a spring hangingverticaiiy, causes its length toincrease by 20 mm. What isthe mass required to stretch itby 35 mm'lA 3509B 2009The extension of a springvaries rvith the loaci hungfrom it as shorvn in the graphin Diagram 31.

l-

; arervhatf the:50 g

1

I

dwthree:d as

3

(c)(c) How long does it take before the objectstarted on its retum journey to the startingpoint?

ll markl(d) What is the velocity of the object at stage

P?

12 marksl(e) What is the velocity of the object on its

retum iourney during stage R'J

[2 markslA What is the displacernent of the object at the

end ofits journey?

11 markl(g) Sketch a velocity-time graplr to show the

motion of the object.

f? nnrksfDiagram 2 shows a section of ticker tape obtainedfrom the motion of a battery-driven toy car usinga ticker-timer of frequency 50 Hz.

fell:e ofa'l

,rn,n of

-qrkl

near:ted.onal

Diagram 6. I shows a wooden block of 2.0 kg mifssis at rest on a piece ofrough plank. The plank isplaced on a horizontal floor.

Wooden blockPlank

DIAGRAM 6.1

(a) In Diagram 6.1, draw and label an affow orarrows to fepresent the forces acting on thewooden block.

fi narkl(b) The plank is then slowly lifted at one end

while the other remained in contact with thefloor. The wooden block remained stationaryas shown in Diagram 6.2.

In Diagram 6.2, dratv and label arrowsto represent all the forces acting on thewooden block.

[2 marksl(ii) Are the forces acting in Diagram 6.2 in

equilibrium? Explain.

[2 marksl(c) When the angle. 0, is greater than 40", the

block accelerales down the plank.What canbe deduced about the forces acting on thewooden block?

[2 marks]After recess, two students, X and Y, of 60 kg masseach rvent back to the same classrcom on thesecond floor. Both of them move from the sameposition on the ground ffoor but took ditl'erentroutes as shown in Diagram 7. Student X walksstraight up while student Y takes a long walk.[Assumeg= l0ms-2]

",ffrr to/hate?

arklthe

orklthe

tion

urklthe

ieldr'l

a

e

lassrnlytlie

II

I

?l

DIAGRAM 6.2

Key:

-

Routeofstudentx----- RouteofstudentY

I'IAGRAM 7(a) (i) What is the magnitude of the forceexerted by studentX in carrying himselfup the stairs?

[2 marks](ii) What is the work done by student X?

(iii) What is the work done by "rrf":Tt

12 marksl(iv) Based on the answers in 7(a)(ii) and

7(a)(ii1), compare the work done bythese two students.

(b) fl mark)

Student X takes 60 s while student Y takesI50 s to reach the classroom.(i) What is the power of student X?

[.] marle](ii) What is the power of student Y /

fi narklA lift rated 100 kW can carry12 passengers of 80 kg each to a height of6.0 m in 3 s. What is the efficiency of thernotor used in the lift?

(c)

f2 marksl

titis

\arkfan beTIOVCarksl\ctrkl

ctrksl

:tion.o the(It'k.tlif the

al'ksf

ou,thtree.

(iii) Name the physics principle that expl4lns the above phenomenon. I ntarkl(b) Foodstuffs such as chilli, onion and garlic can be pounded using a mortar and a pestle. Explain how the

foodstuffs can be crushed easily using these two apparafus. 13 tnarksf(c) Diagram 9.3 shows some of the safety features that are built into a car.

Rear crumple zone

Front crumple zone

Using relevant physics principles, explain why these safety features are necessary.fl0 marksf

i

Section AAnswer all queslions.

I An experiment is set up to investigate how the weight, W, of an object depends onits mass. m, when the object is brought near to the Earth's surface. The arrangementof the apparatus is shown in Diagram 1.1.At the beginning of the experiment, a 50 g plasticine ball is tied up to a smallpieceof match stick rvith a string. The plasticine ball is then hung onto the hook of thespring balance. The reading of the spring balance, W, is shown inDiagraml.2.The cxperirnent is repeated by using plasticine balls rvith masses, m, 100 g, 150g, 200 g, 250 g and 300 g. The readings of the spring baiance, W, are showti itiDiagrams 1.3. 1.4, L5, 1.6 and 1.7.

rn= l00gDI.{GRAM T.3

Springbalance

IH=titJI

,-: Irn: 150 g

DIAGRAM I.4

,H=tit

=l"

=tm:200 g

:3:t=t=t4-l

m=3009DIAGR-{Mrark)

I thebrcea'ksl

DIAGRAII1.5

(a) Forthe experiment described above,(i.1 the manipuiated variable:

m=250gDTAGRAM I.6

identi$

1.7

Headrest

DIACRA]II9.3

DIAGRAM I.1

m=509DIAGRANI l.2

/,J fl markf