as ocr mechanics questions

7/24/2019 As OCR Mechanics questions

1/167

1. Draw a line from each unit on the left-hand side to the correct equivalent unit on theright-hand side.

j o u l e ( J )

k g m s 2

w a t t ( W )

m

n e w t o n ( )

J s !

"#otal 2 marks$

2. #his question is a%out estimating the &ressure e'erted % a &erson wearing shoesstanding on a floor see the figure %elow.

(i) *stimate the weight in newtons of a &erson.

weight + ......................................................

"!$

Villiers High School 1


2/167

(ii) *stimate the total area of contact in square metres %etween the shoes of this&erson and the floor.

area + .................................................... m2

"!$

(iii) ,ence estimate the &ressure in &ascals e'erted % this &erson standing on thefloor.

&ressure + .................................................... a

"!$

"#otal marks$

3. #he figure %elow shows two masses Aand Btied to the ends of a length of string. #hestring &asses over a &ulle. #he mass Ais held at rest on the floor.

B! . / 0 k g

A! . 2 0 k g

2 . 1 0 m

f l o o r

& u l l e

#he mass Ais !.20 kg and the mass Bis !./0 kg.



3/167

(a) alculate the weight of mass B.

weight + ......................................................

"!$

(%) 3ass Bis initiall at rest at a height of 2.10 m a%ove the floor. 3ass Ais then

released. 3ass Bhas a constant downward acceleration of !.04 m s2

. 5ssumethat air resistance and the friction %etween the &ulle and the string arenegligi%le.

(i) 6n terms of forces e'&lain wh the acceleration of the mass Bis less thanthe acceleration of free fall g.

................................................................................................................

................................................................................................................

"!$

(ii) alculate the time taken for the mass Bto fall !.70 m.

time + ...................................................... s

"$

(iii) alculate the velocit of mass Bafter falling !.70 m.

velocit + ................................................ m s!

"2$



4/167

(iv) 3ass Bhits the floor at a s&eed of 2.78 m s!

. 6t reboundswith a s&eed of

!./0 m s!

. #he time of contact with the floor is .0 9 !02

s. alculate themagnitude of the average acceleration of mass Bduring its im&act with thefloor.

acceleration + ................................................ m s2

"2$

"#otal 4 marks$

4. 5 lift has a mass of /00 kg. 6t is designed to carr a ma'imum of 1 &eo&le of total mass

/:0 kg. #he lift is su&&orted % a steel ca%le of cross-sectional area .1 9 !07

m2.

When the lift is at ground floor level the ca%le is at its ma'imum length of !70 m as

shown in the figure %elow. #he mass &er unit length of the ca%le is .0 kg m!

.

P

g r o u n d f l o o r

l i f t s h a f t

s t e e l c a % l e

! 7 0 m



5/167

(a) ;how that the mass of the !70 m long steel ca%le is 720 kg.

"!$

(%) (i) #he lift with its 1 &assengers is stationar at the ground floor level. #he

initial u&ward acceleration of the lift and the ca%le is !.1 m s2

. ;how that

the maximumtension in the ca%le at &oint Pis !.8 9 !07.

"7$

(ii) alculate the ma'imum stress in the ca%le.

stress + .................................................... a

"2$

"#otal 8 marks$



6/167

5. 5n electron in a &article accelerator e'&eriences a constant force. 5ccording to onestudent the acceleration of the electron should remain constant %ecause the ratio offorce to mass does not change. 6n realit e'&eriments show that the acceleration of theelectron decreases as its velocit increases. Descri%e what can %e deduced from suche'&eriments a%out the nature of accelerated electrons.

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"#otal 2 marks$

6. #he figure %elow shows the velocit vector for a &article moving at an angle of !< tothe hori=ontal.

! n the figure a%ove show the hori=ontal (x-direction) and vertical (y-direction)com&onents of the velocit.

"2$



7/167

(ii) alculate the hori=ontal (x-direction) com&onent of the velocit.

velocit + ................................................ m s!

"!$

"#otal marks$

7. #he figure %elow shows a shi& S%eing &ulled % two tug-%oats.

/ / n the figure a%ove draw an arrow to show the direction of the acceleration ofthe water at &oint P.(3ark this arrow A).

"!$

(%) Descri%e the energ conversion that takes &lace as the water travels from theend of the hose &i&e to the ground.

I yo!r "s#er$ yo! sho!l% !se "&&ro&ri"te techic"l terms$ s&elle% correctly'

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"2$



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(c) *'&lain wh the hori=ontal com&onent of the velocit remains constant at

8.0 m s!

.

.........................................................................................................................

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.........................................................................................................................

"!$

(d) ;how that the water takes a%out 0./ s to travel from the end of the &i&e to theground.

"!$

(e) ;how that the s&eed of the water when it hits the ground is 1.: m s!.

"$"#otal 1 marks$



24/167

19. Define the e#to.

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"#otal ! mark$

20. ;tate wh the equation G) + m" cannot %e a&&lied to &articles travelling at s&eeds verclose to the s&eed of light.

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"#otal ! mark$

21. #he figure %elow shows the hori=ontal forces acting on a car of mass 400 kg when it istravelling at a &articular velocit on a level road.

#he total forward force %etween the tres and the road is 200 and the air resistance(drag) is 10 .



25/167

(i) alculate the acceleration of the car.

acceleration + ................................................ m s2

"2$

(ii) *'&lain wh we cannot use the equation v + ! "t to &redict the velocit of thecar at a later time even when the forward force is constant.

.........................................................................................................................

.........................................................................................................................

"!$

"#otal marks$



26/167

22. #he figure %elow shows a &erson %eing lifted verticall u&wards % a ro&e.

* r o & e

#he mass of the &erson is 82 kg. #he u&ward vertical acceleration of the &erson is

!.7 m s2

.alculate the tension * in the ro&e.

* + ......................................................

"#otal marks$

23. Define tor(!e o+ " co!&le.

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"#otal ! mark$



27/167

24. (a) *'&lain wh momet o+ " +orce and tor(!e o+ " co!&le have the same unit m.

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"!$

(%) #he figure %elow shows an irregular sha&ed metal &late of constant thicknessthat can swing freel a%out &oint P.

P

0 . 0 m

0 . 7 0 m

: . 0

(i) #he weight of the &late is :.0 . With the &late in the &osition as shown in

the figure calculate the clockwise moment of the weight of the &late a%outan a'is through &oint P.

moment + .................................................. m

"!$



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(ii) *'&lain wh the moment of the weight reduces to =ero when the &latereaches the %ottom of the swing.

................................................................................................................

................................................................................................................

"!$

"#otal marks$

25. Descri%e an e'&eriment to determine the centre of gravit of the metal &late shown inthe figure %elow.

P

0 . 0 m

0 . 7 0 m

: . 0

..................................................................................................................................

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"#otal marks$



29/167

26. #he figure %elow shows a section of the human forearm in equili%rium.

o % j e c t

% i c e &

e l % o w

! 7 c m

. / c m

2 c m ! 1

: 0

B

#he weight of the o%ject in the hand is :0 . #he centre of gravit of this o%ject is2 cm from the el%ow. #he %ice& &rovides an u&ward force of magnitude ). #hedistance %etween the line of action of this force and the el%ow is ./ cm. #he weight ofthe forearm is !1 . #he distance %etween the centre of gravit of the forearm and theel%ow is !7 cm.

H taking moments a%out the el%ow determine the magnitude of the force ) &rovided% the %ice&.

) + ......................................................

"#otal marks$



30/167

27. #he figure %elow shows a 20 force acting at an angle of 1< to the hori=ontal.

1 ne &ossi%le reason wh our answer to (c)(i) is smaller than the acce&ted

value of 4.1! m s2

is the reaction time of the student. ;tate another reason

wh the answer is smaller than 4.1! m s2

.

................................................................................................................

................................................................................................................

"!$

"#otal 8 marks$



39/167

38. 5 skdiver jum&s from a stationar hot-air %alloon several kilometres a%ove the ground.

(a) 6n terms of acceleration and forces e'&lain the motion of the skdiver

immediate$&after jum&ing ...............................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

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.........................................................................................................................

at a time be'oreterminal velocit is reached ...................................................

.........................................................................................................................

.........................................................................................................................

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.........................................................................................................................

atterminal velocit. ..........................................................................................

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.........................................................................................................................

":$



40/167

(%) 6n the final stage of the fall the skdiver is falling through air at a constant s&eed.#he skdivers kinetic energ does not change even though there is a decreasein the gravitational &otential energ. ;tate what ha&&ens to this loss ofgravitational &otential energ.

.........................................................................................................................

.........................................................................................................................

"!$

(c) #he figure %elow shows a sketch gra&h of the variation of the velocit v of theskdiver with time t.

v C m s

t C s

/ 0

2 /

0

02 0! 00

- !

;uggest the changes to the gra&h of the figure a%ove if an for a more massive(heavier) skdiver of the same sha&e.

.........................................................................................................................

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"2$

"#otal 4 marks$

39. Define #ork %oe % a force.

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"#otal 2 marks$



41/167

40. Define&o#er.

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"#otal ! mark$

41. *'&lain wh the efficienc of a mechanical device can never %e !00@.

..................................................................................................................................

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"#otal ! mark$

42. 5 car has a total mass of 1!0 kg. 6ts s&eed changes from =ero to 0 m s!

in a time of!2 s.

(i) alculate the change in the kinetic energ of the car.

change in kinetic energ + ....................................................... J

"2$



42/167

(ii) alculate the average &ower generated % the car engine. 5ssume that the&ower generated % the engine of the car is entirel used in increasing the kineticenerg of the car.

&ower + ......................................................W

"!$

(iii) #he actual efficienc of the car is 2/@. #he car takes !1 kg of &etrol to fill its

tank. #he energ &rovided &er kilogram of &etrol is 7: 3J kg!

. #he drag force

acting on the car at a constant s&eed of 0 m s!

is /00 .

! alculate the work done against the drag force &er second.

work done &er second + .................................................. J s!

"!$



43/167

2 alculate the total distance the car can travel on a full tank of &etrol when

travelling at a constant s&eed of 0 m s!

.

distance + ......................................................m

"$

"#otal 8 marks$

43. #he figure %elow shows a wooden %lock motionless on an inclined ram&.

% l o c kr a m &

,

#he angle %etween the ram& and the hori=ontal is -.

(i) #he weight , of the %lock is alread shown on the figure. om&lete the diagram% showing the normal contact (reaction) force . and the frictional force ) actingon the %lock

"2$

(ii) Write an equation to show how ) is related to , and -'

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.........................................................................................................................

"!$

"#otal marks$



44/167

44. #he figure %elow shows a kitchen cu&%oard securel mounted to a vertical wall. #hecu&%oard rests on a su&&ort at A.

w a l l

B

s u & & o r t

s c r e w

c u & % o a r d

8 / c m

! 2 c m

2 0 0

5

#he total weight of the cu&%oard and its contents is 200 . #he line of action of itsweight is at a distance of !2 cm from A. #he screw securing the cu&%oard to the wall isat a vertical distance of 8/ cm from A.

(i) ;tate the &rinci&le of moments.


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.........................................................................................................................

"2$



45/167

(ii) #he direction of the force ) &rovided % the screw on the cu&%oard is hori=ontalas shown in the figure a%ove. #ake moments a%out A. Determine the value of ).

) + ......................................................

"2$

(iii) #he cross-sectional area under the head of the screw in contact with the

cu&%oard is :.0 9 !0/

m2. alculate the &ressure on the cu&%oard under the

screw head.

&ressure + .....................................................a

"2$

(iv) ;tate and e'&lain how our answer to (iii) would change if at all if the samescrew was secured much closer to A.

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"2$

"#otal 1 marks$



46/167

45. 6n Be%ruar !444 5;5 launched its ;tardust s&acecraft on a mission to collect dust

&articles from the comet #em&el !. 5fter a journe of /.0 9 !0!2

m that took :.4 ears;tardust returned to *arth with sam&les of the dust &articles em%edded in a s&eciallow-densit gel. When a dust &article hits the gel it %uries itself in the gel creating a

cone-sha&ed track as shown in the figure %elow. #he length of the track is t&icall 200times the diameter of the dust &article.

g e l

c o n e - s h a & e d t r a c k

n o t t o s # a $ e

(a) alculate the average s&eed in m s!

of ;tardust during its voage.

s&eed + .................................................m s!

"2$



47/167

(%) alculate the average sto&&ing force &roduced % the gel for a dust &article of

diameter 0.80 mm and mass 7.0 9 !0:

kg travelling at a velocit of

:.! 9 !0m s

!relative to ;tardust.

force + .......................................................

"$

"#otal / marks$

46. >n the a'es of the figure %elow sketch a stress against strain gra&h for a t&ical ductilematerial.

s t r e s s

0

s t r a i n0

"#otal 2 marks$

47. ircle from the list %elow a material that is ductile.

jell co&&er ceramic glass

"#otal ! mark$



48/167

48. Define !ltim"te tesile stregth of a material.

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"#otal ! mark$

49. ;tate Hooke/s l"#.

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"#otal ! mark$

50. #he figure %elow shows a mechanism for firing a ta%le tennis %all verticall into the air.

% a l l & l a t f o r m

s & r i n g

& l a t e

& u l l a n d r e l e a s et o f i r e % a l l

s & r i n g f i ' e dt o & l a t e



49/167

#he s&ring has a force constant of 8/ m!

. #he %all is &laced on the &latform at theto& of the s&ring.

(i) #he s&ring is com&ressed % 0.01/ m % &ulling the &latform. alculate the forcee'erted % the com&ressed s&ring on the %all immediate$&after the s&ring isreleased. 5ssume %oth the s&ring and the &latform have negligi%le mass.

force + .......................................................

"2$

(ii) #he mass of the %all is 2./ 9 !0

kg. alculate the initial acceleration of the %all.

acceleration + .................................................m s2

"!$



50/167

(iii) alculate the ma'imum height that could %e gained % the %all. 5ssume all theelastic &otential energ of the s&ring is converted into gravitational &otentialenerg of the %all.

height + ......................................................m

"$

"#otal : marks$

51. (i) Define s&ee%of an o%ject. *'&lain how ou would determine the constant s&eedof a conker at the end of length of string %eing whirled in a hori=ontal circle.

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"$

(ii) Define velocityof an o%ject.


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"!$



51/167

(iii) H reference to s&eed and velocit e'&lain the difference %etween a scalarquantit and a vector quantit using as an e'am&le the terms s&ee%and velocity.

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"2$

"#otal : marks$

52. Big. ! shows a long ro&e that is tied at one end to a high su&&ort. 5 girl swings forwards

and %ackwards across a &ool using the other end of the ro&e.

B A

s u & & o r t

r o & e

Fig. 1



52/167

Big.2 shows the variation with time t of the dis&lacementx of the girl fromA to B and %ack to A.

2 . /

2 . 0

! . /

! . 0

0 . /

00 ! . 0 2 . 0 . 0 7 . 0 / . 0 : . 0

x C m

tC s

Fig. 2

(i) ;tate what the gradient of the gra&h re&resents and e'&lain wh the gra&h shows%oth &ositive and negative gradients.

.........................................................................................................................

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.........................................................................................................................

"2$

(ii) 3ark on Big.2 with a cross a &osition where the s&eed of the girl is =ero(la%el this ().

"!$



53/167

(iii) !. *'&lain how ou can determine using Bigure 2 that the ma'imum s&eed of the

girl is a%out !.7ms!

.

.........................................................................................................................

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2. *stimate the uncertaint in the value of the ma'imum s&eed o%tained in thiswa.

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"2$

"#otal / marks$

53. (a) Define "cceler"tio.

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........................................................................................................................."!$



54/167

(%) 5n aircraft of total mass !./ 9 !0/kg accelerates at ma'imum thrust from the

engines from rest along a runwa for 2/ s reaching the required take-off s&eed

of :/ m s!

.

5ssume that the acceleration of the aircraft is constant. alculate

(i) the net force acting on the aircraft to &roduce this acceleration

force + .....................................

"$

(ii) the distance travelled % the aircraft in this time.

distance + ................................. m

"2$

(c) 5t a &articular air&ort the length of the runwa for the same take-off s&eed is lessthan our answer in (%)(iii). ;tate and e'&lain what change could %e made to theaircraft to ena%le it to reach the required take-off s&eed on this shorter runwa.

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"2$

"#otal 1 marks$



55/167

54. (a) Define

(i) &o#er

................................................................................................................

................................................................................................................

"!$

(ii) a o!le'

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"!$

(%) 5 force )acts on an o%ject. #he o%ject moves at an angle M to this force. *'&lainwh the work done ,% the force in the direction of motion of the o%ject is notjust

,+ )x

%ut is equal to

,+ )xcos-

6n our answer ou should use a&&ro&riate technical terms s&elled correctl.

.........................................................................................................................

.........................................................................................................................

"!$

"#otal marks$



56/167

55. #he diagram %elow shows a &art of a fairground ride with a carriage on rails.

3 0 o

3 . 9 m

#he carriage of mass /00 kg is travelling towards a slo&e inclined at 0< to thehori=ontal. #he carriage has a kinetic energ of 2/ kJ at the %ottom of the slo&e. #hecarriage comes to rest after travelling u& the slo&e to a vertical height of .4 m.

(i) ;how that the gravitational &otential energ gained % the carriage is !4 kJ.

"2$

(ii) alculate the total work done against the resistive forces as the carriage movesu& the slo&e.

work done + ........................................... kJ

"!$



57/167

(iii) alculate the magnitude of the resistive force acting against the carriage as itmoves u& the slo&e.

resistive force + .......................................

"2$

"#otal / marks$

56. (a) ;tate ,ookes law.

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"2$



58/167

(%) #he diagram %elow shows the variation of the a&&lied force ) with the e'tensionx for a &articular s&ring.

' o r # e ) *

e x t e n s i o n )

x + x 1 0 , 3 m -

! 2

! 0

1

:

7

2

00 2 0 7 0 : 0 1 0 ! 0 0

(i) ?se the diagram to determine the force constant of the s&ring.

force constant + .................................. m!

"2$



59/167

(ii) Determine the elastic &otential energ stored in the s&ring when a force of20 is a&&lied.

energ stored + ......................................... J

"2$

(iii) ;tate one assum&tion made in our calculation of the energ in (ii).

................................................................................................................

................................................................................................................

"!$

(iv) #he energ stored in the s&ring is used to &ro&el a metal %all of mass mhori=ontall. #here is !00@ transfer of energ from the s&ring to the %all.;how how the s&eed v of the metal %all is &ro&ortional to the e'tensionxof

the s&ring. Bind the constant of &ro&ortionalit.

................................................................................................................

................................................................................................................

................................................................................................................

"2$

"#otal 4 marks$



60/167

57. *'&lain the following terms in relation to motion of a road vehicle.

(i) r"kig %ist"ce

.........................................................................................................................

.........................................................................................................................

"!$

(ii) thikig %ist"ce

.........................................................................................................................

.........................................................................................................................

"!$

"#otal 2 marks$

58. 5 car of mass 100 kg is travelling at a s&eed of 20 m s!

. alculate

(i) the kinetic energ of the car

kinetic energ + ......................................... J

"2$

(ii) the deceleration of the car when the %raking distance is 27 m.

deceleration + ...................................... m s2

"2$

"#otal 7 marks$



61/167

59. Descri%e in terms of the forces acting on the driver how wearing a seat %elt and havingan air%ag in a car can hel& to &rotect the driver from injur in a head on collision.

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"#otal 7 marks$



62/167


63/167

(%) #he diagram %elow shows a com&uter resting on a ta%leto& that is hinged at&oint A.

0 . 1 0 m

c o m & u t e r

t a % l e t o &

2 0 0

0 . 2 / m

)

5 H

#he ta%leto& has a mass of /.0 kg and its centre of gravit is 0.70 m from the a'isof the hinge A. #he com&uter has a weight of 200 acting through a &oint 0.2/m from the hinge A. #he ta%leto& is su&&orted to maintain it in a hori=ontal&osition % a force ) acting verticall at B. #he distance 5H is 0.10 m.

alculate the force ) a&&lied at B that is required to maintain the ta%leto& inequili%rium.

force ) + ..................................................

"$

(c) *'&lain wh the force ) and the 200 force shown in the figure a%ove cannot %ea cou&le.

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"!$

"#otal : marks$



64/167

62. (a) Define the o!g mo%!l!sof a material.

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"!$

(%) *'&lain wh the quantit strain has no units.

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"!$

"#otal 2 marks$

63. (a) *'&lain what is meant % a %rittle material.

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"!$

(%) Define the ultimate tensile strength of a material. ;uggest wh an engineerdesigning a sus&ension %ridge should know the value of this quantit for all hismaterials.

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"2$

"#otal marks$



65/167

64. #he figure %elow shows the &ath of a %all thrown from Aand &assing through &ositionsB %and .

#he %all is thrown from Awith a velocit v. 5 vector arrow on the figure. re&resents themagnitude and direction of the velocit of the %all at A.

(a) >n the figure draw arrows to re&resent the hori=ontal and vertical com&onents ofthe velocit of the %all at A.

"!$

(%) ;tate how the com&onents of the velocit of the %all at B %and com&are withthe com&onents at A. 5ssume air resistance is negligi%le.

(i) #he vertical com&onent at B ............................................................

#he hori=ontal com&onent at B .........................................................

"!$

(ii) #he vertical com&onent at % ...............................................................

#he hori=ontal com&onent at % .........................................................

"!$

(iii) #he vertical com&onent at ............................................................

#he hori=ontal com&onent at .........................................................

"!$



66/167

(c) *'&lain the answers ou have given for the com&onents of the velocit of the %allat &ositions B %and .

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"7$

"#otal 1 marks$

65. *'&lain with reference to a car the quantities

(i) r"kig +orce

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"!$

(ii) r"kig %ist"ce'

.........................................................................................................................

.........................................................................................................................

........................................................................................................................."!$

"#otal 2 marks$



67/167

66. 5 car of mass !10 kg travelling at !.! m s!

is %rought to rest % the %rakes in71.2 m. alculate

(i) the initial kinetic energ of the car

kinetic energ + .............................. J

"$

(ii) the average deceleration of the car

deceleration + .............................. m s2

"2$

(iii) the average %raking force.

%raking force + ..............................

"2$

"#otal 8 marks$

67. Define the quantities

(i) #ork

.........................................................................................................................

........................................................................................................................."!$



68/167

(ii) &o#er.

.........................................................................................................................

.........................................................................................................................

"!$

"#otal 2 marks$

68. #he figure %elow shows a crane that is used to move heav o%jects.

#he motor in the crane lifts a total mass of !/00 kg through a height of 2/ m at a

constant velocit of !.: m s!

.

alculate

(i) the tension in the lifting ca%le

tension + ..............................

"2$

(ii) the time taken for the mass to %e raised through the height of 2/ m

time + .............................. s

"!$



69/167

(iii) the rate of gain of &otential energ of the mass

rate of gain of &otential energ + .............................. J s!

"$

(iv) the minimum out&ut &ower of the motor used to raise the mass.

&ower + .............................. W

"!$

"#otal 8 marks$

69. Define

(i) the mometof a force

.........................................................................................................................

.........................................................................................................................

"2$

(ii) the tor(!eof a cou&le.

.........................................................................................................................

.........................................................................................................................

"!$

"#otal marks$



70/167

70. #he figure %elow shows a uniform rectangular %eam su&&orted % two stra&s. #he%eam is in equili%rium.

0 . / 0 m

w e i g h t + : 0 0

A B

3 2

! . 0 m

7 . 0 m

#he weight of the %eam is :00 and its length is 7.0 m. #he stra& Ais &ositioned0./0 m from one end of the %eam and the stra& Bis &ositioned !.0 m from the otherend.

(i) 1 ?se the &rinci&le of moments to show that the u&ward forceat stra& 5 is!770 .

"2$

2 ,ence determine the force at the stra& B.

force + ..............................

"2$

(ii) Discuss whether the forcesand &rovide a cou&le.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"2$



71/167

(iii) #he area of stra& Ain contact with the underside of the %eam is 2. !02

m2.

alculate the average &ressure e'erted on the %eam % stra& A.

&ressure + .............................. unit ..............................

"$"#otal 4 marks$

71. Define the quantities

(i) stress

.........................................................................................................................

"!$

(ii) str"i'

.........................................................................................................................

"!$

"#otal 2 marks$

72. #he results given in the ta%le %elow are o%tained in an e'&eriment to determine theEoung modulus of a metal in the form of a wire. #he wire is loaded in ste&s of /.0 u& to 2/.0 and then unloaded.

loading unloading

load C e'tension C mm e'tension Cmm

0.0 0.00 0.00

/.0 0.27 0.27

!0.0 0.78 0.71

!/.0 0.8! 0.8!

20.0 0.4: 0.4/

2/.0 !.20 !.20



72/167

(i) ?sing the results in the ta%le and without &lotting a gra&h state and e'&lainwhether the deformation of the wire

1 is &lastic or elastic

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"!$

2 o%es ,ookes law.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"2$

(ii) *'&lain how the e'tension and length of the wire ma %e determinede'&erimentall.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"2$

(iii) #he wire tested is !.82 m long and has a cross-sectional area of !.10 !08

m2.

?se the e'tension value given in the ta%le for a load of 2/.0 to calculate theEoung modulus of the metal of the wire.

Eoung modulus + .............................. a

"$

"#otal 1 marks$



73/167

73. 6n this question two marks are availa%le for the qualit of written communication.

Helow is a gra&h of the dis&lacement against time for the motion of a radio-controlledmodel car.

0 / ! 0 ! / 2 00

! 0

d i s & l a c e m e n t

C m

t i m e C s

2 0

0

?se the gra&h to descri%e and e'&lain without calculation



74/167

(a) how the velocit changes from time t+ 0 to time t+ 20 s

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"/$



75/167

(%) how the acceleration changes from time t+ 0 to time t+ 20 s.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"7$

Oualit of Written ommunication "2$

"#otal !! marks$

74. 5 cham&ion H3P cclist wishes to %ecome a &rofessional and seeks hel& from an 5-level hsics student in creating an act. #he student suggests two stuntsQ one involvinga hori=ontal take-off on to a slo&ing ram& and the other involving a loo&-the-loo&manoeuvre.

(a) #he student %egins % finding out the ma'imum s&eed the cclist can &roduce onlevel ground. #wo flags are &ositioned 270 m a&art on a flat road. #he cclist is

told to accelerate to the first flag and to &edal as hard as he can until the secondflag is &assed. #his is shown in Big. !

2 7 0 m

Fig. 1



76/167

#he student gets the cclist to re&eat the test three times and records thefollowing resultsF

!7.1 s !8.2 s !/.: s

;how that the mean s&eed the cclist can maintain over the 270 m is a%out

!/ m s!

.

"2$

(%) #he student designs the stunt shown in Big. 2 where the cclist must take off at

!/ m s!

from a hori=ontal launch &ad and land smoothl just at the edge of aslo&ing ram&.

l a u n c h & a d

r a m &

g r o u n d7 / ne valuehas %een given.

energ at the to& C J energ at the %ottom C J

gravitational &otential energof jum&er

0

kinetic energ of jum&er

elastic &otential energ ofelastic ro&e

"$



96/167

(%) #he elastic ro&e %eing used has an unstretched length of /0 m and s&ring

constant of 27 m!

. alculate the tension in the ro&e when the jum&er sto&s atthe %ottom.

tension + ....................................................

"!$

(c) Bor a ro&e o%eing ,ookes law show that the elastic &otential energ stored inthe ro&e is given %

E + 2

!

kx2

where k is the elastic s&ring constant andx is the e'tension.

"2$

(d) (i) 5nother jum&er has a mass of !00 kg. Bor this %ungee jum& a ro&e of

unstretched length 7/ m and a s&ring constant 2:.8 m!

is used. ;howthat this data is valid for the same !/0 m fall %efore sto&&ing for the firsttime.

"2$



97/167

(ii) 6n fact the ro&e used % the second jum&er is a shorter length of the ro&eused % the first jum&er. *'&lain wh the s&ring constant for the shorterro&e is larger.

...............................................................................................................

...............................................................................................................

...............................................................................................................

"!$

"#otal 4 marks$

89. #he figure %elow illustrates a conveor %elt for trans&orting oung children u& a snow-covered %ank so that the can ski %ack down.



98/167

5 child of mass 20 kg travels u& the conveor %elt at a constant s&eed. #he distancetravelled u& the slo&e is 27 m and the time taken is // s. #he vertical height clim%ed inthis time is 7.0 m.

(a) Bor the child on the conveor %elt calculate

(i) her s&eed

s&eed + ............................ m s!

"2$

(ii) her kinetic energ

kinetic energ + ............................ J

"2$

(iii) the increase in her &otential energ for the com&lete journe u& the slo&e.

&otential energ + ............................ J

"2$

(%) (i) #he conveor %elt is designed to take a ma'imum of !/ children at an onetime. alculate the &ower needed to lift !/ children of average mass 20 kgthrough a height of 7.0 m in // s.

&ower + ............................ W

"2$

(ii) #he %elt is driven % an electric motor. ;tate toreasons wh the motorneeds a greater out&ut &ower than that calculated in +b-+i-.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

"2$

"#otal !0 marks$



99/167

90. (i) Define velocity'

.........................................................................................................................

.........................................................................................................................

"!$

(ii) Define "cceler"tio'

.........................................................................................................................

.........................................................................................................................

"!$

"#otal 2 marks$



100/167

91. Big. ! shows a ruler clam&ed at one end. 5 mass is attached to the other end of theruler and is then made to oscillate u& and down.

B

Am a s s

Fig. 1

Big. 2 shows the variation with time tof the velocit vof the mass as it oscillates fromAto Band %ack to A.

7 . 0

2 . 0

v C c m s

0 0 . 2 0 0 . 1 00 . ! 0 0 . 2 0 0 . 0 0 . 7 0 0 . / 0 0 . : 0 0 . 8 0 0 . 1 0

A B At C s

7 . 0

2 . 0

!

Fig. 2

(i) Bor the gra&h shown in Big. 2 state what is re&resented %

! the area %etween the gra&h and the time a'is

.........................................................................................................................

"!$

2 the gradient of the gra&h at a &articular time.

.........................................................................................................................

"!$



101/167

(ii) ?se Big. 2 to determine the distance travelled % the mass from time t+ 0 totime t+ 0.20 s.

distance + ............................ cm

"2$

(iii) ?se Big. 2 to descri%e how the acceleration of the mass varies as the massmoves from Ato B.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"2$

(iv) ?se Big. 2 to calculate the average acceleration of the mass %etweent+ 0.2/ s and t+ 0.// s.

acceleration + ............................ cm s2

"2$

"#otal 1 marks$

92. (i) Define&ress!re'

.........................................................................................................................

.........................................................................................................................

"!$



102/167

(ii) Define momet o+ " +orce.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

"!$

"#otal 2 marks$

93. (a) #he figure %elow shows a device used for com&ressing materials.

1 0 m m ! 2 0 m m

+ 2 0

l e v e r a r m& l u n g e r

c r u s h e d m a t e r i a l

c l i n d e r

c r o s s - s e c t i o n a l

a r e a

7 . 0 ' ! 0 m 2

F

4

5 vertical force Fof 20 is a&&lied at one end of a lever sstem. #he lever is&ivoted a%out a hinge . #he &lunger com&resses the material in the clinder.

(i) #wo forces acting on the lever arm are its weight and the force F. >n thefigure a%ove draw and la%el toother forces acting on the lever arm.

"2$

(ii) H taking moments a%out show that the force acting on the &lunger is1 . #he weight of the lever arm ma %e neglected.

"2$



103/167

(%) (i) #he cross-sectional area of the &lunger is 7.0 !0

m2. alculate the

&ressure e'erted % the &lunger on the material in the clinder.

&ressure + ............................ a

"2$

(ii) ;tate tomethods of increasing the &ressure e'erted % the &lunger.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

"2$

"#otal 1 marks$

94. #he figure %elow shows three ro&es attached to a ring . #hree clinders x &and are su&&orted % these ro&es from two &ulles.

x

&

6

5

: 0 / + 7 / 0

4 0

as ocr mechanics questions

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