mechanics 1 test 10_11 answers

8/4/2019 Mechanics 1 test 10_11 answers

1/23

AMERICAN ACADEMY LARNACAVI PHYSICS: SEMESTER 1: TEST 1 [Date: ]

BLANI{PAGETURN OVER FOR QUESTION 1

... /2


2/23

SECTION AAnswer ALL questions.

For questions 1-10, in Section A, select one answer from A to D and put a cross in the box 1 2 S I .Ifyou change your mind, put a line through the box ~ and then

mark your new answer with a cross 1 2 S I .1 Which of the following is a scalar quantity?

[J A displacementB force

K I C timeE J D velocity

.__ __ ,,__ . ''_ ' ___ ..__f!,otal for Question 1 = _ . ! mark)~ A force of 24 N and a force of 15N act at right angles to each other.

The size of their resultant force is[J A 15.8NnL:.IiI~i-------------.I~ 3 A bus is travelling at a speed of 9.0 m S-I. It then accelerates at a rate of 0.75 m S-2 for atime of 8.0 s. What is its final speed?

B 24.3 NC 28.3ND 39.0N

________ .~(T;;;.o;:._t..:..;,a;:._l:::..:o:..::.r_Q~u,estion= 1 mark) _

[J A 6 . 0 m S - 1~ B 15 m S - 1[] C 17 m S - ILJ D 21 m S - 1

(Total for Question 3 = 1mark)


3/23

4 A person is standing at point B in a train carriage travelling round a sharp bend to theright. The person jumps up. Nearest which marked point is the person most likely toland?

Direction of bend

~ AE 3 BLJ cLJ D

(Total for Question 4 = 1 mark)


4/23

5 Which of the following is not a SI base quantity?~ A force0 B length0 C mass0 D time

___ ___,_(Totalor Q uestion-f-= 1 m ark-< ,.)_6 ' The diagram shows the forces acting on a picture, of weight W, suspended by a cord.

The tension in the cord is T.

T T

W

Which of the following expressions shows the correct relationship between W and T?D A W= 2 T cos eE J B W=Tcos e0 c W = T sin e~ D W = 2 T sin O

(Total for Question ({ = 1 m ark )

"...S


5/23

-5-; : r - A person weighing 100 N stands on some bathroom scales in a lift. If the scales show a

reading of 110 N, which answer could describe the motion of the lift?l X l A Moving downwards and decelerating.C J B Moving downwards with a constant velocity.C J C Moving upwards and decelerating.C J D Moving upwards with a constant velocity.

_._,--------_._-----I S A ball is thrown straight up in the air and caught when it comes down. Which graph

best shows the velocity of the ball from the moment it is released until just before it iscaught?Velocity Velocity

A Timeime B

Velocity Velocity

cTimeime

D

C J A C J C [] D

----_ _ . - - - - - - - - - - - - - - (Total for Question f ? = 1mark)

... b


6/23

Use the diagram below for questions 9 and 10.The diagram shows four forces acting on an aeroplane.

Lift

Thrust

Weight~I 9 Which of the following shows the correct two relationships if the aeroplane is climbingI at a constant velocity?! r Relations~~_~ __ _ j Relationship 2 - - 1i lj I-A--l---li-ft->-weight -+I--_-_-_-t-_hrust>rag - - J

-~ B I lift> weight thrust ~ drag JI ----t- + 1 1 - - - - __j,i!E J C I lift =weight thrust> drag I[- ~ I~_I_~ L ~ ~ _ ~eight I __hrust =_dra~_j

(Total for Question 9 = 1 mark)'---"--'---.------.! 10 The aeroplane is now flown at a constant altitude but an increasing speed.Ii~I~~r~Ii!---- -_._-_._---",,_._'"-_._.-i TOTAL FOR SECTION A = 10 MARKS~ff&fli. !ijI I~I I

Which of the following pairs of forces will have the same magnitude?A drag and weight

o B drag and thrustC lift and dragD lift and weight

. (~ot~ ..for Question 10 = ~~ark)


7/23

-1-SECTION B

Answer all questions in this section.There are ' 1 1 - marks in this section.

~ Figure J shows the variation of the speed, v, of a sprinter with time, t, from the time thestarting pistol is fired until the sprinter reaches the finishing line during a 1 0 0m sprint.

Figure t .

~

_L+ t " ! t ! - - ~ - i - + - - I+H-+H-H++,+ ,H,-++;-++ +-+ H/.. . - r++ iH-I+i- , rH++H rr t " ir - - i -H- t " i f t E E E E t t E E B ~ ~ ! t . : , i $ t E ! E ' E ' t E t E d d ~ 1 1 l l l ~ l t 'I /. ! - ! . - - d - : : rt, ,I = 1 : : P , : t11 -, ~ i : , , . t-Fttf-~-t-

1-+++-i_H_++~i " ' - " - . n : ~ - + - '- l- t- H -H .- I+ - I- H + + : : - H f - - H f - - ' 'L=-H-+-+- I - l - l - l -bl .-1 0 .1

. : . . 1 :~ ; r t i : ' , : , - + j t , ::ttt9 ' I i . . ' . r + + - + '! I m - + . . .t -++ -1 - r - -H++- " -1. I i j I - t - -, I

8httttiittt1l ' Iflr' i I , t m g t t t t : ! : 'W ' H $ 'i I- t t tt' t : ~ = t + t t I -H- i++ -+++++- I - - - I -+ - , ' r+ ' ,.- ~ i I! i : i7 H-f- I+Hr- , + . il- +H- !...,.' +.+:+I++I- i -H-I -+-+Hr-Hr- l r+H,-H,+!-+++,+++-I - -+- I - - j - I " ' i - i - I -H+++++++!++;- l -~I - i - I - i - , Hi-r !H- I -H - fH -H ,- + !- +++ , +++ -1 - 4-+-H-H- l - l - l++++-H--H-+++-I - - i - I -Hr- - I -H i- l - l++ ' ,

6 ' -_~H_f- l ._-+_:~~,_:_:! : ,' + - ' , + i 1 -1+H+ ;,-H -H -+ ': I + + , ' + - rt -t-i- I: : ,: : : :. : - : --+L +- i-+H+ ..+ + + f - ' - I + ,- t-i-5 u i : I j i i ! - 1 = + 1 = ' + 1 + t + + + = l = i : t P = 1 H = 1 = t + : t tLL .. ,! . j -I' i i : 1.1...' L

,-H'+'l'+'++-Y--- I I, ~ ~ ' J ' J ' M i j t I Wi :~r ' t~ ' : '~~'Iii ! ! I i ! : ! I I I'II I, -n-rr"".i, i ! ,-1-+++ -tt :I -H-+h-H-H-~- I -mH+- ,1 \-[--1'-[-[--- ! ! I -H I -" TH- l- H -f -

i, ; I ! iiI3 ! I; ! i ! ; i I I,.+I- ' ' " 1 , ' - ' - -'-K- H- l - l - l - H-H+++++f - ++++ f - -+: n = ; , j - '= j++- i -++ 'H- i- - I -H- i-+- I L . . J . . .: c i H-~- H I , - , " - -I , "l0---

12v/ms-1

!! I

4

7 8 93 4 1 0ti s1 5(a) Explain why the graph does not go through the origin.

. f f )~.~ I fO.1Iri.~~tf:!r~..... t ~ . ; . .~ . ./.f.!f~ :~~ .....- . ~ t.~ ~ 7 :.f. ~ ~ ~ .~ p . : M : . .(1 mark)


8/23

- & -(b) Determine the acceleration of the sprinter 3.5 s after the start of the race.

Give an appropriate unit for your answer.a l : : Ar I =:: 4 P - J < e . J : d3.Sf"35r 1l/3.('r (j ) I::: ~=~J. ~- 3~~ hA.1'_-~ s: . 2 . . . 1:::.tJt'3w-2.. O .'f.3A ,.__ '2 ...acceleration r . . .

(3marks)(c) What distance was covered inthe first 2.0s of the race?

distance 1 1 .& .(4 marks)

(d) Describe briefly how the data for the sprinter's velocity-time graph shown in Figure 2could have been collected .. . . . .~ C J . k : . . 4 , ~~(;! f 1 . . If , . .' : 1 . ! .a x : : . ..( ':'!/~ ~ .4 .~.:r.4~r.~ ~. . . . . . . . . .?~~ t ? 6..~~ q.~:~.~.~.6.~ ~.~ .) .............f . . e . . 4 : ( ~fl~.~4...f.~.......~ ..- f4 '": . f .{~~*'.3 < . ~ .4 i w ~ { . + .: . . .. .~. . . : : . " k ; . : ~ ~ ; . : : ; : : ~ : ; ~ : ~ ; ; ; . : ~ . : ; ; ; , . : : ; t : . : ~ : ; : : ; ; . . : ~ i 1 j ~ f j f f : j g ~ : 5 r ~ ! ~ ~ ~ ! t ~._,. .- _ . ,.__ ._ . .: ' _ . __. , _ . _ . . _ . , i!_~_~~!Lorue~!io~.{L~fe_~.~~!L...._

" '/J


9/23

* I~YOu are asked to determine the acceleration of free fall at the surface of the Earth, g,using a free fall method in the laboratory.(a) Describe the apparatus you would use, the measurements you would take and explain

how you would use them to determine g.

J~ fwNc.~ ~ . ~ W ; : J t A . u J : . . . . . . . . .. . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .7......~..~ r~ J I J J i ' f t . ( a ( ; c t . . a~......................................................................................................... y . ., ; ~ 4 tA f ( ~ i t . J J . . ~'~"r-

.t1" ;II\1:: e:................. . " " /. .................................................................................~.~~.~i.~. ... ~..t..3 . . ? : jY ~ . .d..?..~~ : r ..

(b) Give one precaution you would take to ensure the accuracy of your measurements .

. . & l4 f . .. L ~ ~ ( { . .. .~ . . f.(~t....~~~r.:t!..!/(f.~.~.~ ~ 1 ! ;r . . fy . . / . .~ . r ~~ .__ (,-T _o!.~ lor Qu~_~t ion I : z . = 7 marks)

"po


10/23

-10 -,-------------------------------------T---" I Leave ii blank iI '!

l , ~ .. . ./11

A flea jumps vertically from a surface. Itdoes this by rapidly extending its legs so that itexperiences an upward force. Figure 1 shows the flea before it begins its jump. Figure 2shows the flea the moment its legs are fully extended and about to leave the surface.

----------------- ~to .44mmW ~ \ , ~ , ~ ~ - - - - - - - - - - - i - _

Figure 1 Figure 2

(a) Explain how Newton's third law accounts for the upward force produced .

. . . ~ , f. . . . . . .f .4 . g . . . .~ l'f? . . . . .. .~. '!. . . . .D .1 -f(~./4~~~ ..tk./.t:ftfo~~r({F!:J.... ~~(y. : .4 . .~~.&'!.t{ - 1 . A ~~~.~.t.~....b..~!.!!.~f4.e!..~ $..~~.: .

(2)(b) (i) At the moment the flea's legs leave the surface its body is raised 0.44 mm and it

is moving at a speed of 0.95 m s'. Show that the average acceleration of the fleaduring take-off is about 1000 m S-2.. . . . . . . . . . . . . . . .~. : : : : l : < . .~.1:..~ 4 J :. .u u u u : # . u u ' : l :. u ~ . .P u ~ . ; : , , { f , : : . = .0 .l.S..4 ~ : : : : . ( P . ) 'j ' : ! l . . . : ; J ~ u ._2AF . : 1 . ko. Y~X(",- ~.....................................................I .q .~ .~ .~ . .~.~ .. . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . . ... l r ! .P . . . ~ . .~ . ( _ . .~ . .~ . .

(3)(ii) The mass of the flea is 4.0 x 10-7 kg. Calculate the resultant vertical force acting

on the flea .. . F ; . . .z: ;"'i- ..~ f . : l ' .K.:: . ' .


11/23

[ ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ ~ a - a ~ nI (c) (i) What constant force opposes the upward motion of the flea? I..r.~...' !0 . .f . . J f . . . .~ ./ .~ '!:/- !4...~/1 ,~~( . ! :"" ,~ ,~/ , ~ .~~J

. .f . . '1 . t : ( . .J ! f t ~ f ! .:(f( o.{ ~ f ! .& . .~ : .~ .(1)

-1/-

(ii) Air resistance also opposes the motion of the flea. At the instant the flea's legsleave the surface it is travelling at 0.95 m S-1. It takes a further 9.3 x 10-2 S toreach its maximum height. Calculate the change in height it achieves during thistime. Assume its deceleration is constant ..Ar.?.~ 9 - A f . . . . - s P . . . 4 J . f . : " . l f f}'-f. -~.1.:}k'-;..............................................................:?:..q: t ! ! . .t.f. ~ ................................................................. ~ ..~.:~.~~ .

Change in height =......q....q_ .~ . f :.~ . .. .. .. .. .(3)

(Total 10 marks)

... 11:t


12/23

.._-------,I Leave!~ b ~ 1If; A gardener tilts a wheelbarrow of weight W by applying a total upward force F to its I Ihandles. The diagram shows the forces acting on the wheelbarrow. R is the normal Ireaction (contact) force acting on the wheeL

-I):

(1)

(1)

pF

x

(a) (i) The wheelbarrow is stationary. State an expression that relates R, Wand FW-= -~ fF................................................................................................................................

(ii) Each of these three forces is one of a Newton's third law pair of forces.

Complete the following statements.The force that pairs with R acts on 6 t . . .: :J . I : . f .M , . ! f l . . t . .~ . .The force that pairs with Wacts on ;~ f . . t ! : r . . . f . . 4 . ' : .The force that pairs with F acts on . ; I k ~r . .~ . l ! : I :?~6~d4' : ! .~ .~p

(b) The gardener now pushes the wheelbarrow forward. To do this he must change themagnitude and direction of the force F.(i) Add an arrow to the diagram, at X, to show the approximate direction in which

this force must act. Label this arrow P.

.. -/13


13/23

-/3Leaveblank

(ii) Explain why the magnitude and direction of force F must change when thegardener pushes the wheelbarrow forward ........~p e : : e ! t .~.f...~ k J . h . ' < ! f . . { ~ 0 ; : . . .:


14/23

rI / ~ (a) The enlarged diagram shows a circular copper disc. Ithas a diameter of 30 mm andI a thickness of 5.0 rnrn.-/{t---------------------.-----~---.--\ Leave I

blank II

Density of copper =8900 kg m'. . . . . . . ~ h , r a _ ~ ( ~ J i f o ; . ( T l r . . ~ : t ) ( ? ~.s(Tf:f)(f. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . : L ~J.. . . . .~ . .~ - : : . . . .7 J ! .. .+..~....~.~.k/.?~.~.h.f. . , < j . . ~ . ~ . . . . > . ;' :2 ~ . Q ? " . " "k l - r J. ../ Y Iu . -f...................................................................: K ..8 . . .(..(l..~.1r.~.~.1 - - /

=O3/tV

Circularcopperdisc : : : : ) . .~----- 30 rnrn -----~ 15.0m ee fShow that the weight of the disc is about 0.3 N.

..........................................................................................................................................~ 0.3 JI/................ ..._.. ~y. .

(3)

'------- __ ---1__j~.//s


15/23

- - - - - - - - 1 L~~~~ " " iblank i,,

-15-(b) (i) State Newton's first law of motion...A ... ... . 1 7 . . . ._ I ~ : ~ ( <


16/23

I j A kite is held by a string and flies because of lift produced by the flow of air.Lift

Not to scale

Drag

WeightTension

Figure 1 Figure 2Figure 2 shows a free-body force diagram for the kite.(a) Sketch a labelled vector diagram to show that the four forces are in equilibrium.

(1)

- . 11 l-


17/23

-/1-(b) The lift is 4.3 N, the drag is 6.0 N and the weight is 0.44 N.

Calculate the tension in the string. State its magnitude and direction from thehorizontal.

.....1)r.h! ~ ~ ?) !j :;'.=h ! ..~.f. ..~ tV . .~ (!'f({!J!. .- = 3e c 1 1 /...Ik ..~])=f 0I V....T=f1)..1:]J~::::/{,:~p./ +~. r 6==t1A J

. . . .. .. .. .. .. J ) i r ~ ~ , p ~ . . : . . fa ~... .~.. T t . . :=.... '3.V , ~ . . .,=.O~{~r k ('OM'Magnitude of tension = ..... " : f ~ / I !

:3 < 9 , t"Direction of tension from the horizontal =. -c~--.-,,-------.--------~---------------. (To ta l f or Ques tion} '"; ;: .5 J!larkL _

"18


18/23

-18-This question is about trains on the London underground rail system.(a) Fig. 1 - 'fj.1 shows two maps of the same part of the London underground.

Fig. f ' f .1 A is part of the 'traditional' tube map that is used by travellers every day.Fig. 1; .1 B shows the actual positions of the stations and rail track.

Edgware BakerPaddington Road Marylebone Street

Fig.I1v.1A Fig. It.1B

[1]

Fig. '1'f;.1(i) The average speed of the train between stations is fairly constant. Explain how a

passenger travelling from Paddington to Marylebone could tell that Edgware Road isactually closer to Marylebone (Fig. /i.1 B) than to Paddington (Fig. In.1A).: I - E tJ/ l( fz.~ Jk~ - 6 ~ s a f.t, . . . 1 0 fr~ 1$.J.1~1~* t-~1U~~ ~ 1 i - - J t t . . . C f . o -4j to 1t~ F~Wd:"~ /C'cJ..

. f . . e ' 7 J A If.5' , e t 2 h 6H . e .(ii) Fig. l=t.1A shows thatthe track between Baker Street and Regent's Park consists of

three straight line segments joined by quite sharp curves.A passenger, who is not able to see out of the window, is travelling between these stationsat a steady speed. Suggest and explain how she could tell that the continuous curve ofFig.IJt.1 B is actually the correct arrangement.~ f 4;//tZl,!.,)'-4ir t"J"{R ~e.fL.e 0n:fo.

tAJ.../ri .~ 1 . 1 l . ;(tlt. A JU i.e e lA,J . e: " 4 ~ I ~dtt(a. ~4(iii) Suggest why the 'traditional' tube map of Fig. 11.1A has remained popular since its

design by Harry Beck in 1933, even though it is not an accurate representation of thepositions of the stations and the directions of the lines.:[" -{ (f ecrre- -~ r.ad./eAI/~ f- u-e/c{pr~r24lMrf< l f ' l f~.

[2]

[1]

.. .1 19


19/23

-19-

(b) Many of the stations on the London underground rail system are higher than the track eitherside of the station (Fig. 11-.2).

J a a Tnot to scale station platform

Fig. 1f.2(i) The angle a between the track and the horizontal on each side of this station platform

is 1.Show that the component of the train's weight acting parallel to the track whenapproaching or leaving the station is about one-fiftieth of its weight.

You may draw a vector diagram to help your answer.I I I L J _ V f i C A . e -Wg--~ h ll I_ _ : = . { f k if

W , / ' "=frLt=-0(1- ~ O o l . . = - J 4 r z ](ii) Describe the effect of this force on the motion of the train when approaching, and whenleaving, the station.h ' 4 e 4 4(1 1 m . . e l . . . . ' : : J : ' f r . t r / 4 4 J " 1/ . e c e (e" ,a.{eW '4 e it t e 4. . u / t t . . J : i r & " " ~ 4)/~ 4 i C . e cA. -t ' .erev. f - (iii) At each station the train has to stop and then start again. Explain why the arrangement

of Fig./?- .2 wastes less energy, as compared with having the station on a perfectly leveltrack.4 pLY f~ f7 ~v.e e ~t: : : -c . I e . WI tt / fA . v - r { r . A e " Y A 1 : . .1 : . ;,('8 Il . e ~ r et.c- tJ/ (kc: - ; ; > / ,& 6 - f ) a4J. t -~t . tt f . . " T- W .= }JtI4.

~ - r : : = J u d t f i + ~ } - ;::Ju(tt-t'J-) ,- = - I{)O '1(Y-o - I - t:f'-- = = /.1)do ~v(t) At a later time, the helicopter is moving forward in level flight at a constant velocity of50mS-1. The cable carrying the vehicle now hangs at a steady angle of 15 to thevertical as shown.

vertical

T: /ehlilJ4W : W Ij4f/f".f j_ : 'r:;;l a , r rt-flft

(i) On U J - , I t ' 9 . , draw arrows showing the forces acting on the vehicle. Name theseforces on the diagram.

(ii) Calculate the tension in the cable in this case.

(Total for Questions 18=10marks)

.. .1 22


22/23

. . . . . . . . . . . . . . ., f ; ; . c j " - : c : J ! : " I . .v : . " ' ~ t!f.~ 4~ ~ ..~.{!F: "'.~l.1i.~t( ~l[t'

. . . . . . . . . . . . .A ! 'r : c~(X!.t"!., t;.~ zli0:4t ~..l!?..b:

'= 0 + 2 . _ X t.r t b . t r --1.kS u ;- S ~1: ~T=- ' f - . 1 - 1 M . - r - /- f"L '7'

1 & A skydiver accelerates towards the ground at 9.81 m S-2 at the instant that he leaves theaeroplane.(a) Explain why his acceleration will decrease as he continues to fall.

~!IJ/rl,"'~J~,gf,,)q,;r~~:!I'de/_t


23/23

-23-

/ L.= O ra t H t.j - _ _

Figure tA student, mass 80 kg, stands on a horizontal set of bathroom scales, of negligiblemass, attached to a massless platform that slides down a 30 incline, Figure I. The

. scales read 75 kg. Calculate:(i) the vertical acceleration a; of the student(ii) the acceleration of the student down the slope as(iii) the coefficient of dynamic friction J .1 between the platform and the slope, whereJ .1 is the ratio of the frictional force to the normal reaction.N o ' fa '_ : , /CA4,t ;I:.F=AI-/f)

mechanics 1 test 10_11 answers

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