mechanics 1 test 10_11

8/4/2019 Mechanics 1 test 10_11

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

NAME I IGRADE I

BLANI(PAGETURN OVER FOR QUESTION 1

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-2-SECTION A

Answer ALL questions,For questions 1-10, in Section A, select one answer from A to D and put a cross in the box~,

Ifyou change your mind, put a line through the box ~ and thenmark your new answer with a cross ~.

1 Which of the following is a scalar quantity?L J A displacementU B forceL J C timeD D velocity

~ A force of 24 N and a force of 15N act at right angles to each other.The size of their resultant force isU A 15.8N

B 24.3 NC 28.3 ND 39.0N

____ ..._._.__ . ._''_''_.__ .__~_._._ ,,~. (Total for ..Q!!"estio~2 =_!..!!!a~~)_,. __,.,_"3 A bus is travelling at a speed of9.0 m S-I. It then accelerates at a rate of 0.75 m S-2 for a

time of 8.0 s. What is its final speed?o A 6.0ms-1

B 15 m S-1o C 17 m S-1o D 21 m S-1

____ (~T_o_,talor Questi~!!} = 1 mark)

.~. 3


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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

o Ao Bo Co D


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5 Which of the following is not a SI base quantity?D A forceD B length

C massD time

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

Which of the following expressions shows the correct relationship between W and T?

---__ . .__ ._-- .._--_._._._------

A W= 2 Tcos 8D B W=Tcos 8D C W=Tsin8D D W = 2 T sin 8

... 'S


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

reading of 110 N, which answer could describe the motion of the lift?o A Moving downwards and decelerating.o B Moving downwards with a constant velocity.

C Moving upwards and decelerating.D Moving upwards with a constant velocity.

8 A ball is thrown straight up in the air and caught when it comes down. Which graphbest shows the velocity of the ball from the moment it is released until just before it iscaught?Velocity Velocity

A Timeime B

Velocity Velocity

C Timeime D

0 A 0 B D C 0 D______________ ~(T _o_ta_l_foruesti~n g'= 1 mark) _

. . ' / 6 " "


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

Lift

Thrust

Weight

9 Which of the following shows the correct two relationships if the aeroplane is climbingat a constant velocity?

Relationship 1 Relationship 2" . _ " - " " - " l--~""""---"-"--------"-"-A lift> weight thrust> drag

lift> weight thrust = drag,

lift = weight thrust> drag

L J D lift = weight thrust = drag

10 The aeroplane is now flown at a constant altitude but an increasing speed.Which of the following pairs of forces will have the same magnitude?L J A drag and weightD B drag and thrustD C lift and dragD D lift and weight

TOTAL FOR SECTION A = 10 MARKS

... / : : ; .


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-1-SECTION B

Answer all questions in this section.There are ttl- marks in this section.

~ Figure I 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 100 m sprint.

Figure I ,

1 1

7654

2

6 7 8 9 10tis

1 2 3 4 5

(a) Explain why the graph does not go through the origin.

(1 mark).. '/8


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

Give an appropriate unit for your answer.

acceleration .(3marks)-

(2) What distance was covered in the first 2.0s of the race?

distance .(4 marks)

(d) Describe briefly how the data for the sprinter's velocity-time graph shown in Figure 2could have been collected.

(2 marks)

. . . / :>


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*/~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.

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


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r - - - - - - - - - -I I~I

-10 -

(2)

(3)

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.

Figure 1 Figure 2(a) Explain how Newton's third law accounts for the upward force produced.

(b) (i) At the moment the flea's legs leave the surface its body is raised 0.44 mm and itis moving at a speed of 0.95 m S-I. Show that the average acceleration of the fleaduring take-off is about 1000 m S-2.

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

Resultant vertical force = .(1)

.. -/11

Le~;elblank


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-11-(c) (i) What constant force opposes the upward motion of the flea?

(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-I. It takes a further 9.3 x 10-2s toreach its maximum height. Calculate the change in height it achieves during thistime. Assume its deceleration is constant.,................................................................................................................................

Change in height = .(3)

(Total 10 marks)

(1)

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-/;L-

(1)

(3)

(1)

r "I~ A gardener tilts a wheelbarrow of weight W by applying a total upward force F to itshandles. The diagram shows the forces acting on the wheelbarrow. R is the normalreaction (contact) force acting on the wheel.

F

x

(a) (i) The wheelbarrow is stationary. State an expression that relates R, Wand F

(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 .The force that pairs with W acts on .The force that pairs with F acts on

(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 whichthis force must act. Label this arrow P.

, . -/13


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-/3-1 ---------------------- - - - - - - - - - - - - ~ : ~ ; nI (ii) Explain why the magnitude and direction of force F must change when the I! gardener pushes the wheelbarrow forward. I

I

................................................................................................................................. _ " , ' _ , _- , - _ - __ .. -- (3)(Total 8 marks)


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-/f--IJ (a) The enlarged diagram shows a circular copper disc. It has a diameter of 30 mm anda thickness of 5.0mm.

Circularcopperdisc

Show that the weight of the disc is about 0.3 N.

15.0 mm

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

(3)

,------------------------------------- -----p /t'S

Density of copper =8900 kg m-3

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

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

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

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'----------------------------------------------------------------------~-~.~-, .//b

-15-(b) (i) State Newton's first law of motion.

(ii) Two copper discs as described in part (a) of the question are placed on top of oneanother as shown in the diagram below.

Figure 1 and Figure 2 are free-body force diagrams which show the resultant upwardand the resultant downward forces acting on the discs A and B respectively. Label themagnitude of the forces P, Q, X and Y.

Figure 1 (Disc A)

!P, magnitude = NA Q,magnitude ~ NFigure 2 (Disc B)

B I X , magmtude ~ NY, magnitude - N

(iii) A force F forms a Newton's third law pair with the force Q.State the following:

magnitude of F = .direction of F = .type of force = .object upon which Facts = .

(4)(Total 11 marks)

(2)

(2)


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/~ 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 1Figure 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.

Figure 2

- . /Il-


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-/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.

Magnitude of tension = .Direction of tension from the horizontal = ...

(Total for _Qu~!!!~~t9-==_~~!E!t_~" .. ' - " " " " -" - -- - - - - .. - , , , , , . - - , , - . . . . . ""-----~.------ .. . - , - , , .. '".,-.- ..-~---"-"-" '~~,.,. . . . '---'-,----------'"''''.~~.---.-"--,-~.-".-'"~-,,---,..-.- .. -'"-----'".,,~.-~.. ,-.-,-.-"--~~.

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-18-I~ This question is about trains on the London underground rail system.

(a) Fig. J tf.1 shows two maps of the same part of the London underground.Fig. 1 ' 1 ' . 1 A is part of the 'traditional' tube map that is used by travellers every day.Fig. I f . 1 B shows the actual positions of the stations and rail track.

Edgware BakerPaddingon Road Marylebone Street

Fig. fl.1BFig.llJ.1

(i) The average speed of the train between stations is fairly constant. Explain how apassenger travelling from Paddington to Marylebone could tell that Edgware Road isactually closer to Marylebone (Flq. li.1H) than to Paddington (Fig. In.1A).

(ii) Fig. (i=.1 A shows that the track between Baker Street and Regent's Park consists ofthree 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.I"f,.1 B is actually the correct arrangement.

(iii) Suggest why the 'traditional' tube map of Fig. Ii- .1A has remained popular since itsdesign by Harry Beck in 1933, even though it is not an accurate representation of thepositions of the stations and the directions of the lines.

[1]

[2]

[1]

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-19-

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

tube train

_-Jij--'::--:==-- ~~/~-'station platform o rnot to scaleF ig . 1 1 -.2

(l) The angle 0 between the track and the horizontal on each side of this station platformis 10ShoW 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.

,[2](ii) Describe the effect of this force on the motion of the train when approaching, and when

leaving, the station.

(iii) At each station the train has to stop and then start again. Explain why the arrangementof Fig. if .2 wastes less energy, as compared with having the station on a perfectly leveltrack.

(Total for Questions 17= 10marks)

[2]

[2]

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-20-

I ~ This question is about using a helicopter to transport a heavy load.

50 m steel cable

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-21-A vehicle is suspended beneath a helicopter on a steel cable.(a) The helicopter lifts the vehicle of mass 1500 kg at a vertical acceleration of 3.0 m s-2.

Show that the tension in the cable is 1.9 x 104N.g = 9.8 N kg-i.

(g) At a later time, the helicopter is moving forward in level flight at a constant velocity of50 m S-1. The cable carrying the vehicle now hangs at a steady angle of 15 to thevertical as shown.

vertical

(I) On f : k - , I t " : / . , 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 = 10 marks)

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/~ 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.

(b) The skydiver opens his parachute. Explain why he reaches a terminal velocityshortly afterwards.

(c) The velocity at which he then hits the ground is similar to that achieved when fallingfreely from a height of 3 m. Calculate this velocity.

Velocity = .


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2~* 1~

30IFigure J

A 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 a s(iii) the coefficient of dynamic friction pbetween the platform and the slope, where

J 1 is the ratio of the frictional force to the normal reaction.

(Total for Question 20 = 10 marks)

mechanics 1 test 10_11

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