Ch-(02)Mechanics Revision MC Test

Physics - Revision Test (Mechanics) Time allowed: 2 hours Multiple Choice Questions 1

2

Find the total distance traveled by the boy.

A.

31.41 m

B.

51.41 m

C.

11.41 m

D.

41.41 m

The following is a displacement-time graph of a ping-pong ball that is released from a height of 1 m above a table with zero initial speed. The ping-pong ball bounces for several times.

Neglecting the air resistance, which point in the graph represents the second bounce?

3

A.

E

B.

F

C.

G

D.

H

John is going to his friend’s home but he loses his way. He phones his friend, and his friend told him “ when you arrived at the supermarket, just turn right and walk for 400 metres. That is my home.” In this conservation, what quantity is used? (1)

Direction

(2)

Displacement

(3)

Coordinate of the origin

(4)

Acceleration

A.

(1) only

B.

(2) only

C.

(1), (2) and (3) only

D.

(4) only

(02)Mechanics Revision MC Test.doc

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If there is no air friction, a raindrop falls freely from rest under the action of gravity from the cloud 1 800 m above Hong Kong can have incredible speed. Find the speed before it hits the ground and try to think whether it is dangerous or not.

5

6

A.

189.7 m s−1. It is dangerous.

B.

200 m s−1. It is dangerous.

C.

165.6 m s−1. It is not dangerous.

D.

70.5 m s−1. It is not dangerous.

Which of the following is a vector quantity? A.

The magnitude of acceleration due to gravity

B.

Distance

C.

Speed

D.

Instantaneous acceleration

A runner runs 4 km towards south in 0.5 hr and 5 km towards east in 1.5 hr. What is his average speed?

7

A.

4.50 km h−1

B.

5.67 km h−1

C.

20.50 km h−1

D.

5.00 km h−1

A ball rolls down an inclined runway and then travels on a smooth table. Which of the following velocity-time graphs correctly describes the motion of the ball? A.

B.

C.

D.

(02)Mechanics Revision MC Test.doc

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8

The diagram shows the acceleration-time graph of two cars traveling on a straight road. Which of the following statements is/are CORRECT?

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(1)

Two cars have the same speed at time C.

(2)

Two cars have travelled the same distance from time C to D.

(3)

Car A has a larger acceleration than car B at time E.

A.

(1) only

B.

(3) only

C.

(2) and (3) only

D.

(1), (2) and (3)

A mass is moving on a track. The track is composed of two regions, region A is a smooth inclined plane and region B is a rough horizontal plane. The following is the ticker tape for the motion of the mass from region A to B. Estimate the deceleration of the car in region B. Given that the frequency of the ticker tape timer is 50 Hz.

A.

10 m s−2

B.

2 m s−2

C.

3 m s−2

D.

5 m s−2

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10 Which of the following graphs correctly describes the motion of a free falling object, which is initially at rest? (s = displacement, v = velocity, t = time) A.

B.

C.

D.

11 A ball is put on an inclined plane with an adjustable angle. If we increase the angle from 0° to 90°, which of the following statements is CORRECT? A.

The acceleration of the ball along the inclined plane is a constant value for different angles.

B.

The ball moves at uniform speed for different angles.

C.

The acceleration due to gravity of the ball changes for different angles.

D.

The acceleration of the ball along the inclined plane changes for different angles. (02)Mechanics Revision MC Test.doc

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12 The following is the displacement-time graph of an object. Which of the following graphs is its corresponding velocity-time graph? (Given that v = 0 and s = 0 at t = 0.)

A.

B.

C.

D.

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13 In order to get the atmospheric data from the sky, equipments are sometimes tight to a balloon and let it to rise to the expected height. However due the low atmospheric pressure in the sky, the balloon will explode and the equipments will fall freely after some time. Which of the following velocity-time graphs correctly describes the motion of the equipments when the balloon explodes. Assuming there is no air resistance and takes the downward direction as negative. Also v > 0 when t = 0. A.

B.

C.

D.

14 A KCR train takes 8 minutes from rest to travel from Mongkok to Shatin. The distance between the two stations is 7.4 km. According to the given information, which of the following is CORRECT? A.

The instantaneous speed is 15.4 m s−1.

B.

The instantaneous acceleration is 10 m s−2.

C.

The average speed is 15.4 m s−1.

D.

The average acceleration is 10 m s−2. (02)Mechanics Revision MC Test.doc

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15 The record of 100 m running in boys in certain school is 11.01 second. What physical quantity can we get from the information? A.

The average speed

B.

The instantaneous speed

C.

The average acceleration

D.

The instantaneous acceleration

16 A car is moving uniformly on a road and a dog suddenly appears at t = 0 in front of the car at a distance d m. When the driver sees the dog, he brakes the car immediately and having the following velocity-time graph. The car stops at a distance 1 m from the dog. Find d.

A.

22 m

B.

15 m

C.

29 m

D.

28 m

17 Heavier objects always fall faster than lighter objects in air. Which of the following statements is/are CORRECT explanation? (1)

There are some external forces acting on the objects, for example, the air friction.

(2)

A heavier object has a larger uniform velocity when it falls freely.

(3)

A heavier object has a larger acceleration due to gravity.

A.

(1) only

B.

(2) only

C.

(2) and (3) only

D.

(1), (2) and (3)

18 Which of the following cases is/are NOT a uniformly accelerated motion? (1)

A feather falls from a certain height inside a vacuum tube.

(2)

A ball rolls along a frictionless plane at uniform speed.

(3)

A coin falls from a certain height in air but air resistance is negligible.

A.

(1) only

B.

(2) only

C.

(1) and (2) only

D.

(2) and (3) only (02)Mechanics Revision MC Test.doc

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19 A ping-pong ball is released from a height of 1 m above a table with zero initial speed. It bounces for several times. Neglecting the air resistance, which of the following graph represents the corresponding displacement-time graph? A.

B.

C.

D.

(02)Mechanics Revision MC Test.doc

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20 A bead is dropping in medium 1 with a uniform speed of 1 m s−1 for 2.5 s. Then it enters into air and falls freely under gravity for 2 m. Finally, it enters medium 2 and immediately moves with uniform speed for 1.5 s. Find the total distance the bead has traveled.

A.

10.1 m

B.

20.1 m

C.

14.1 m

D.

15.1 m

21 A bead falls freely from rest (point A) for 2 m and then it enters a viscous medium vertically. When it enters that medium, it moves at uniform speed immediately. The depth of the viscous medium is 1.8 m. Find the total time for the bead to travel from point A to point B.

A.

2.01 s

B.

0.91 s

C.

1.5 s

D.

0.28 s

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22 A ball falls freely under the action of gravity. Provided that all the measurement of the height of the falling ball is measured from the ground level, which of the following displacement-time graphs correctly describe its motion? A.

B.

C.

D.

(02)Mechanics Revision MC Test.doc

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23 Which of the following velocity-time graphs correctly represents the motion of a ball that free fall from certain height and bounces back to its original position. A.

B.

C.

D.

24 A ball that is initially at rest, takes 0.77 s to fall freely at a height of 3 m above the ground. Find the (i) average speed of the whole journey, and (ii) the instantaneous speed just before it hits the ground. A.

(i) 3.9 m s−1

(ii) 7.7 m s−1

B.

(i) 5.0 m s−1

(ii) 8.2 m s−1

C.

(i) 4.5 m s−1

(ii) 9.2 m s−1

D.

(i) 3.1 m s−1

(ii) 10.3 m s−1

(02)Mechanics Revision MC Test.doc

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25 Which of the following is / are a unit of speed? (1)

m s−1

(2)

km / h

(3)

mile per hour

A.

(1) only

B.

(1) and (2) only

C.

(2) and (3) only

D.

(1), (2) and (3)

26 Graph below shows the displacement-time graph of four objects. Which object is moving at the greatest speed?

A.

Object A

B.

Object B

C.

Object C

D.

Object D

27 Graph below shows the displacement-time graph of four objects. Which object is at rest?

A.

Object A

B.

Object B

C.

Object C

D.

Object D

28 Which of the following statements is/are INCORRECT? (1)

The SI unit of distance is centimeter.

(2)

The SI unit of acceleration is millisecond square.

(3)

The SI unit of speed is millisecond.

A.

(1) only

B.

(2) only

C.

(1) and (2) only

D.

(1), (2) and (3) (02)Mechanics Revision MC Test.doc

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29 Which of the following cases represents a uniformly accelerated motion? (1)

A straight line with constant slope in a displacement-time graph.

(2)

A straight line with constant slope in a velocity-time graph.

(3)

A straight line with constant slope in an acceleration-time graph.

A.

(2) only

B.

(1) and (2) only

C.

(2) and (3) only

D.

(1), (2) and (3)

30 A ball is released at a height of 1.3 m above the ground at an initial speed 1 m s−1. Calculate the speed of the ball just before it hits the ground. (Take g = 10 m s −2.) A.

4.47 m s−1

B.

2.20 m s−1

C.

5.20 m s−1

D.

3.45 m s−1

31 Which of the following statements is/are CORRECT? (1)

The units of distance and displacement are the same.

(2)

We have to define a starting point before using distance or displacement.

(3)

The area under the velocity-time graph represents the distance traveled by a body if it moves along a straight line in one direction only.

A.

(1) only

B.

(3) only

C.

(1) and (2) only

D.

(1), (2) and (3)

32 According to the coin and feather experiment in a VACUUM tube, which of the following statements is/are INCORRECT? (1)

The coin is heavier so that its acceleration is larger.

(2)

The speed of the coin just before it hits the bottom of the tube is larger than that of the feather.

(3)

The distance traveled by the coin is the same as that traveled by the feather in equal time intervals.

A.

(1) only

B.

(2) only

C.

(1) and (2) only

D.

(1), (2) and (3)

33 If there is no reaction force, which of the following cases will occur? (1)

We cannot swim.

(2)

We cannot jump.

(3)

We cannot walk.

A.

(1) only

B.

(2) only

C.

(3) only

D.

(1), (2) and (3)

34 A lift and three men inside have a total mass of 600 kg. If the lift is accelerating upwards with acceleration of 1.1 m s−2, find the tension in the cable of the lift. A.

1 560 N

B.

4 830 N

C.

5 060 N

D.

6 660 N

(02)Mechanics Revision MC Test.doc

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35 A parachutist opens a parachute and an upward force is acting on it. The parachutist and parachute is still accelerating downwards with 1 m s−2. Find the force of air friction given that the mass of the parachutist and parachute is 50 kg and 5 kg respectively. A.

495 N

B.

480 N

C.

470 N

D.

505 N

36 Which of the following statements is / are CORRECT? (1)

Weight depends on the position of objects from the earth.

(2)

Weight depends on the mass of the objects.

(3)

Weight is the same as mass on the earth surface but different on different planets.

(4)

Weight of an object is the same on different planets.

A.

(2) only

B.

(1) and (2) only

C.

(3) and (4) only

D.

(1), (2) and (4) only.

37 An astronaut or a car-racing driver should be able to resist great force because of the extremely great acceleration and deceleration. For example in a rocket racing car match in 1954, the driver decelerated from 1 000 km h−1 to rest in just 1.4 s. Try to estimate the magnitude of the force acting on a 50 kg driver? A.

8 920 N

B.

9 920 N

C.

10 020 N

D.

7 920 N

38 In the deep outer space, there is no gravity at all. If a force acts on an object, it will gain great speed after a considerable of time. Calculate the speed of a 100 g mass if a force of 2 N is acted on it for 2 days. Given that the mass is initially at rest. A.

2.40 × 105 m s−1

B.

3.46 × 106 m s−1

C.

7.38 × 107 m s−1

D.

3.00 × 108 m s−1

39 The figure below shows a grab handle inside a moving train. The train is moving towards left. Which of the statements is CORRECT?

A.

The train is accelerating.

B.

The train is decelerating.

C.

The train is moving with a constant speed.

D.

The status of motion cannot be determined from the figure.

(02)Mechanics Revision MC Test.doc

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40 A man uses a pulley system to slow down the falling of a box. Find the acceleration of the box. Given that the mass of the box is 7 kg and the weight is 5 kg and the string is inextensible.

A.

2.87 N downwards

B.

1.50 N upwards

C.

1.67 N downwards

D.

2.02 N upwards

41 As shown in the figure, a cart is at rest on a frictionless surface. If the fan is turned on, which of the following is/are the CORRECT description?

(1)

The cart will not move.

(2)

The cart will move.

(3)

The cart will move to and fro on the frictionless surface.

A.

(1) only

B.

(2) only

C.

(3) only

D.

None of the above

42 If a parachutist falls freely from an aircraft, which of the following quantities are kept constant? (Assume that air friction is negligible and g is independent of the height from the earth.) A.

Mass only.

B.

Mass and weight.

C.

Mass, weight and acceleration.

D.

Mass, weight, velocity and acceleration.

(02)Mechanics Revision MC Test.doc

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43 A pendulum bob is hung on a fixed end and is pulled aside to a height h. If a peg is put within the path of the bead as shown in the figure, which of the following figures correctly describe the motion of the bead?

A.

B.

C.

D.

44 Which of the following free body diagram represents the point particle is in equilibrium? (1)

(2)

(3)

A.

(1) only

B.

(2) only

C.

(3) only

D.

(1), (2) and (3) (02)Mechanics Revision MC Test.doc

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45 Which of the following statements is / are CORRECT? (1)

The SI unit of force is N.

(2)

The unit of force can be kg m s–2.

(3)

The unit of force can be lb.

A.

(1) only

B.

(1) and (2) only

C.

(1) and (3) only

D.

(1), (2) and (3)

46 Calculate the horizontal component of the resultant force exerted on the ball.

A.

9.28 N to the right

B.

0.62 N to the right

C.

0.62 N to the left

D.

2 N to the right

47 Calculate the resultant force exerted on the mass.

A.

3 N (+x direction)

B.

8.4 N (+y direction)

C.

10 N (vertically upwards)

D.

4.5 N (−x direction)

(02)Mechanics Revision MC Test.doc

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48 The flag is now in equilibrium as shown in the figure. Calculate the value of tension T.

A.

6.88 N

B.

9.2 N

C.

2.37 N

D.

4.73 N

49 As shown in the figure, two forces of 10 N and 17 N are now acting on a point mass A. In order to keep A in equilibrium, what should be the magnitude of the third horizontal force needed to be added?

A.

24 N

B.

27 N

C.

18 N

D.

13 N

50 Newton’s third law of motion can explain which of the following cases? (1)

Galileo’s thought experiment

(2)

Bowling games

(3)

Explosion

A.

(1) only

B.

(2) only

C.

(3) only

D.

None of the above

(02)Mechanics Revision MC Test.doc

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51 In the Galileo’s thought experiment, a ball bearing is allowed to roll on a curtain rail of different curvatures as shown in the figure. What physics concept is demonstrated in this experiment?

A.

Inertia of the ball bearing.

B.

Gravitational force acting on the ball bearing.

C.

Action and reaction pair on the ball bearing and on the rail.

D.

The weight of the bead.

52 Which of the following statements is / are CORRECT? (1)

The weight of a man on the Moon is smaller than that on the Earth.

(2)

The mass of a man is the same on both the Moon and the Earth.

(3)

We cannot determine our own mass in the outer space because there is no gravity.

A.

(1) only

B.

(3) only

C.

(2) and (3) only

D.

(1) and (2) only

53 Which of the following statements is / are CORRECT? (1)

The angle of friction-compensated inclined plane will be different for different objects put on the plane.

(2)

The magnitude of friction depends on the material of the surface.

(3)

Friction does not exist if there is no relative motion between two surfaces.

A.

(1) only

B.

(1) and (2) only

C.

(2) and (3) only

D.

(1), (2) and (3)

54 Which of the following objects is / are acted up by an unbalanced force? (1)

A trolley moving uniformly on a friction-compensated runway.

(2)

A baseball hits by a bat.

(3)

A free falling object.

(4)

A swinging pendulum bob.

A.

(2), (3) and (4) only

B.

(2) and (3) only

C.

(3) only

D.

(1), (2), (3) and (4)

(02)Mechanics Revision MC Test.doc

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55 Estimate the value of the unbalanced force acting on a point mass of 2 kg in time interval AB using the following velocity-time graph.

A.

8N

B.

6N

C.

4N

D.

2N

56 Which of the following cases is / are the CORRECT explanation concerning a point mass, which is accelerating on a friction compensated inclined plane. (1)

There is an unbalanced force acting on the point mass.

(2)

The phenomenon can explain by the Newton’s second law.

(3)

The unbalanced force which cause the acceleration is the gravitational force.

(4)

The unbalanced force which cause the acceleration is the frictional force.

A.

(1) and (2) only

B.

(2) and (3) only

C.

(3) and (4) only

D.

(2), (3) and (4) only

57 In an experiment, boxes slide down and accelerate along a friction-compensated inclined plane. Repeat the experiment using 1 kg, 2 kg and 3 kg boxes, which one will have the greatest acceleration if they are released at the same starting point at rest? A.

1 kg box

B.

2 kg box

C.

3 kg box

D.

They have the same acceleration.

(02)Mechanics Revision MC Test.doc

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58 Two blocks are connected by a string, and are pulled by a force of 5.7 N on a frictionless surface as shown in the figure. If the string breaks suddenly, calculate the acceleration of the heavier block along the plane.

A.

0.87 m s−2

B.

2.60 m s−2

C.

8.66 m s−2

D.

5.00 m s−2

59 Calculate the value of force F if the system is in equilibrium.

A.

1.4 N

B.

1.82 N

C.

0.7 N

D.

3N

60 In the following figure, calculate the value of force exerted on the 1.5 kg block by the 2.5 kg block. Given that all surfaces are frictionless.

A.

25.0 N

B.

28.2 N

C.

27.6 N

D.

19.4 N

(02)Mechanics Revision MC Test.doc

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61 Which of the following cases is / are NOT an action and reaction pair? (1)

Gravitational force acted by Earth on you and the gravitational force acted by you on Earth.

(2)

When hitting a baseball with a bat, the impulsive force acted on the ball by the bat and the impulsive force acted on the bat by the ball.

(3)

When you are standing on the ground. Your weight and the normal force on you.

A.

(1) only

B.

(2) only

C.

(3) only

D.

(2) and (3) only

62 Calculate the value of the air friction if a 1.2 kg ball is dropped under the action of gravity but moving at a uniform speed. A.

20 N

B.

12 N

C.

30 N

D.

16 N

63 In which of the following cases does the bead have the greatest speed just before hitting the ground? A.

B.

C.

D.

(02)Mechanics Revision MC Test.doc

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64 Which of the following statements is / are CORRECT? (1)

Inter-conversion of kinetic energy and potential energy is only valid in the system of roller coaster and simple pendulum.

(2)

A hydroelectric power plants use the inter-conversion of kinetic energy and potential energy to generate electricity.

(3)

We can make use of conservation of energy to create energy.

A.

(2) only

B.

(1) and (2) only

C.

(3) only

D.

(1) and (3) only

65 As shown in the figure, Tarzan travels from one place to another by swinging in the forest. Assume that the rope is just long enough to swing from point A to point B, what is his initial speed in order for him to reach point B?

A.

5.69 m s−1

B.

10.0 m s−1

C.

8.5 m s−1

D.

7.75 m s−1

66 In a circus show, a demonstrator uses a rigid rod to swing from point A in the horizontal direction to point B in the vertical direction as shown in the following figure. What is his initial speed at point A in order to achieve this motion? Given that the rigid rod is 2 m long.

A.

3.06 m s−1

B.

6.32 m s−1

C.

7.74 m s−1

D.

9.85 m s−1

(02)Mechanics Revision MC Test.doc

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67 A pendulum bob of mass 0.1 kg is hung on fixed point A and it is released from rest horizontally. There is a peg 0.1 m directly below point A as shown in the figure. Assume the air resistance is negligible. Calculate is the speed of the pendulum bob at point B?

A.

1.41 m s−1

B.

1.52 m s−1

C.

1.63 m s−1

D.

2.02 m s−1

68 A bead of mass 0.2 kg is released from rest at point A on a wedge of height 1 m. It leaves the wedge at point B. What is the speed of the bead at the moment before it hits the ground?

A.

3.86 m s−1

B.

5.47 m s−1

C.

4.47 m s−1

D.

6.04 m s−1

(02)Mechanics Revision MC Test.doc

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69 A pendulum bob is hung on the ceiling. It is pulled aside to certain height and then released from rest. Which of the following graphs correctly describe the relation between potential energy (PE), kinetic energy (KE), mechanical energy (ME) and time? A.

B.

C.

D.

70 A bead of mass 0.2 kg is released from rest at point A as shown in the figure. In order for it to reach point B and momentarily at rest there, what should be the inclined angle θ of the inclined plane?

A.

50°

B.

45°

C.

30°

D.

20°

(02)Mechanics Revision MC Test.doc

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71 A bead is released at point A with initial speed v as shown in the figure. In order for it to reach point B and momentarily at rest there, what should be the value of v?

A.

3.16 m s−1

B.

4.01 m s−1

C.

1.55 m s−1

D.

2.88 m s−1

72 As shown in the figure, a bead of 0.15 kg is allowed to roll to point C with initial speed of 3.87 m s−1. Due to friction, the bead can only reach a height of 1.5 m on the other side of the track. Find the work done against friction.

A.

0.37 J

B.

1.10 J

C.

0.50 J

D.

1.25 J

73 A string hangs a weight as a pendulum bob. When the weight swings, no work is done on the weight by the tension in the string. Which of the following statements is the correct explanation? A.

Tension is always perpendicular to the direction of motion of the pendulum bob.

B.

Tension is an internal force for the pendulum bob.

C.

Tension is an external force for the pendulum bob.

D.

Since the pendulum is swinging about the axis, total displacement is zero.

74 Which of the following statements is/are CORRECT? (1)

When there is friction, conservation of energy cannot be used because there is energy loss.

(2)

Inter-conversion of kinetic and potential energy is the conservation of energy.

(3)

Kinetic energy and potential energy may be positive or negative but mechanical energy must be positive.

A.

(1) only

B.

(2) only

C.

(3) only

D.

(1), (2) and (3)

(02)Mechanics Revision MC Test.doc

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75 A pendulum bob of mass 0.1 kg is hung on a fixed point with a string. It is released from rest horizontally and it swings to and fro. If the pendulum bob is replaced by another bob of mass 0.5 kg. Which of the following statements is INCORRECT? A.

The two bobs have same speed at the position of release.

B.

The two bobs have same speed at the lowest point.

C.

The two bobs have different speed in the lowest point.

D.

The heavier bob has a larger potential energy than the lighter bob at the position of release.

76 Which of the following cases has/have the greatest increase in potential energy? Assume that the height of each floor is the same. (1)

A 50 kg man uses a lift to move from 2/F to 4/F.

(2)

A 50 kg man runs upstairs from 1/F to 3/F.

(3)

A 50 kg man carries a 5 kg box and walks upstairs from 1/F to 2/F.

A.

(1) only

B.

(1) and (2) only

C.

(3) only

D.

(2) and (3) only

77 A pendulum bob of mass 0.1 kg is hung on a fixed point with a string of length 0.2 m. It is released from rest horizontally and it swings. Assume the air resistance is negligible. Calculate the speed of the pendulum bob at the lowest point as shown in the figure?

A.

1 m s−1

B.

4 m s−1

C.

2 m s−1

D.

3 m s−1

78 A bead of mass 0.2 kg is dropped vertically from a table of height 1 m. Assume the air resistance is negligible and there is no energy loss What is the speed of the bead just before it hits the ground?

A.

6.04 m s−1

B.

4.47 m s−1

C.

2.58 m s−1

D.

5.33 m s−1

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79 Assume that there is no energy loss, calculate the minimum value of initial speed required for the bead to reach point C as shown in the following figure.

A.

2.06 m s−1

B.

5.21 m s−1

C.

3.87 m s−1

D.

4.50 m s−1

80 A ball of mass 0.3 kg released from rest at a height of 2 m. It hits the ground and rebounds to a height of 1.8 m. Calculate the amount of energy dissipated in the process. A.

1.5 J

B.

1.2 J

C.

0.6 J

D.

0.7 J

81 A skier skis down a hill as shown in the figure. Determine his speed when he just leaves point B?

A.

8.75 m s−1

B.

3.26 m s−1

C.

10.95 m s−1

D.

12.90 m s−1

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82 In the forest, there are lots of obstacles. As shown in the figure below, the rope is hinder by a horizontal trunk. If the rope is inextensible, can Tarzan swing to point B if he starts from rest to swing from point A?

A.

Yes, he can rise to the same height.

B.

No, the rope is not long enough.

C.

No, he needs an initial speed.

D.

Not enough information.

83 The law of conservation of energy can be applied to which of the following cases? (1)

Skiing

(2)

Roller coaster

(3)

Riding on a swing

A.

(1) only

B.

(2) only

C.

(3) only

D.

(1), (2) and (3)

84 Which of the following statement is INCORRECT? A.

A swinging pendulum eventually stops because energy is transformed.

B.

The conversions of energies are similar in the cases of roller coaster and pendulum motion.

C.

The conversions of energies are similar in the cases of skiing and a waterfall.

D.

A swinging pendulum eventually stops because law of conservation of energy is invalid.

85 Which of the following statement is INCORRECT? A.

The shape of the roller coaster track in the middle part will not affect the speed of the cart at the lowest position.

B.

A swinging pendulum eventually stops because energy is dissipated.

C.

A ping-pong ball released from a height h can never bounce to a height higher than h whatever the initial speed of the ball.

D.

A ping-pong ball released from rest at a height h will not bounce to a height higher than h.

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86 A bead is used to demonstrate the inter-conversion of kinetic and potential energies in a model roller coaster track. The bead is released at point A with certain speed. Assume that there is no energy loss, which of the following statements is not always true?

A.

It has the highest kinetic energy at point C if the bead can pass point B.

B.

Mechanical energy is always conserved.

C.

Kinetic energy and potential energy is inter-changing.

D.

The velocity of the bead at point B is greater than that at point A.

87 Which of the following statements is/are INCORRECT? (1)

Mechanical energy is the sum of kinetic energy and potential energy.

(2)

Potential energy is a relative quantity. It depends on the choice of reference point.

(3)

Kinetic energy must be positive.

(4)

Potential energy must be positive.

A.

(2) only

B.

(1) and (2) only

C.

(4) only

D.

(3) and (4) only

88 A skier skis down a hill as shown in the figure. Determine his speed just before he lands on the ground?

A.

10.24 m s−1

B.

14.14 m s−1

C.

20.0 m s−1

D.

22.54 m s−1

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89 A skier skis down a hill as shown in the figure. If he wants to increase his speed when he leaves point B. What should he do?

A.

He should ski down from a higher initial position.

B.

He should ski down from a lower initial position.

C.

He should use some lighter equipment so as to decrease his total mass.

D.

He should use some heavy equipment so as to increase his total mass.

90 A 5 kg object is accelerating uniformly with 0.5 m s–2 from rest for 10 s. Find the change of momentum of the object. A.

25 kg m s–1

B.

32 kg m s–1

C.

30 kg m s–1

D.

18 kg m s–1

91 Which of the following quantity represent(s) the unit of force? (1)

J s−1

(2)

kg m s−2

(3)

N

(4)

W m−1 s

A.

(3) only

B.

(2) and (3) only

C.

(2), (3) and (4) only

D.

(1), (2) and (3) only

92 Which of the following designs is/are based on the principle of increasing the impact time during a collision? (1)

Gloves of the baseball players.

(2)

Booster of a rocket.

(3)

The bumper of a car.

(4)

Cushions used by the firemen when an accident breaks out.

(5)

The swinging of a pendulum.

A.

(2) and (3) only

B.

(1), (2) and (3) only

C.

(1), (2), (3) and (4) only

D.

All of the above

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93 Which of the following statements is/are CORRECT? (1)

Conservation of momentum is a result of conservation of energy.

(2)

The Newton’s first law of motion can proof the conservation of momentum.

(3)

When there is an external force, momentum will change accordingly.

A.

(1) only

B.

(2) only

C.

(3) only

D.

(2) and (3) only

94 As shown in the figure below, bob A is hung on the ceiling with a 50 cm string. It is pulled aside to a vertical displacement of 10 cm. It is released from rest and it hits another identical bob B at the lowest position, which is initially at rest. Bob A comes to rest, while bob B will swing up. Find the maximum angle 　reached by bob B, assuming that the collision is an elastic one.

A.

36.9°

B.

53.1°

C.

38.7°

D.

32.5°

95 The figure below shows a Newton’s cradle. How many balls will swing up on the right hand side after the balls on the left hand side are released?

A.

1 ball

B.

2 balls

C.

3 balls

D.

4 balls

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96 A 2 kg stationary block explodes and breaks into two parts as shown in the figure. Find the final speed of the heavier mass.

A.

0.560 m s−1

B.

0.167 m s-1

C

0.615 m s-1

D.

0.205 m s-1

97 Which of the following quantities is/are constant if a ball falls freely from a certain height to the time before it hits the ground. Assuming there is no air friction. (1)

Potential energy of the ball

(2)

Kinetic energy of the ball

(3)

Total mechanical energy of the ball

(4)

Momentum of the ball

A.

(1) only

B.

(2) only

C.

(3) only

D.

(1), (2) and (3) only

98 Block A of 3 kg is moving on a frictionless surface at 5.5 m s−1. Suddenly it hits another identical block B, which is moving at 0.5 m s−1 in the same direction. Find the velocity of A after the collision assuming that the collision is elastic. A.

0.5 m s−1

B.

5.5 m s−1

C.

3.5 m s−1

D.

1.5 m s−1

99 Which of the following statements is/are CORRECT? (1)

The explosion of a bomb is an example of conservation of momentum.

(2)

The bouncing motion of basketball with the ground is a counter example of conservation of momentum.

(3)

Bowling is a game that based on the conservation of momentum.

A.

(1) only

B.

(3) only

C.

(1) and (2) only

D.

(1) and (3) only

100 Which of the following is/are CORRECT? (1)

The momentum of a bowling must be larger than that of a ping-pong ball.

(2)

Dropping an egg to the ground is an example of inelastic collision.

(3)

Conservation of momentum can be used to investigate the speed of cars in car accidents.

A.

(1) only

B.

(2) and (3) only

C.

(1) and (2) only

D.

(1), (2) and (3)

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101 In a car accident, car A of 1 000 kg is hit by car B of 1 580 kg. Car A is initially at rest. From the marking of the tyre on the road, police found that the speed of car A and B after the collision is 10 m s−1 and 8 m s−1 respectively. Find the speed of car B before the collision. (Assume it is valid to use conservation of momentum here.) A.

16.97 m s−1

B.

20.58 m s−1

C.

14.32 m s−1

D.

26.44 m s−1

102 Which of the following quantities does not represent energy? (1)

Mass × acceleration × displacement

(2)

Force × velocity

(3)

Momentum × time × displacement

A.

(1) only

B.

(2) only

C.

(1) and (2) only

D.

(2) and (3) only

103 Car A of mass 500 kg is moving with uniform velocity of 10 m s−1 and having a head on collision with a car B of 500 kg moving with velocity −5 m s−1. Given that the collision is elastic, find the velocity of car B after the collision. A.

10 m s−1

B.

0 m s−1

C.

−5 m s−1

D.

−7 m s−1

104 A 65 g ball moving at uniform horizontal speed of 5 m s−1 is hit by a 10 N force horizontally by a bat. In order for the ball to move a horizontal distance of 20 m in 2 s after the strike, what should be the impact time? A.

0.062 5 s

B.

0.032 5 s

C.

0.802 5 s

D.

0.005 5 s

105 The bumpers of cars should be collapsible in order to reduce the force acting on the car when collisions occur. For a car of 1 000 kg moving with speed 18 m s−1, find the force acting on the car (i) with bumper and (ii) without the bumper. The impact time with and without bumper is 0.05 s and 0.8 s respectively. The car stops after the impact. A.

(i) 360 000 N

(ii) 22 500 N

B.

(i) 420 020 N

(ii) 2 000 N

C.

(i) 560 000 N

(ii) 280 000 N

D.

(i) 220 000 N

(ii) 220 000 N

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106 A force acted on a moving mass suddenly. After that, the horizontal component of the momentum of the mass does not change before and after the acting of the force. Which of the following statements is/are CORRECT? (1)

The force is only acting in the vertical direction.

(2)

Momentum is not conserved in the horizontal direction.

(3)

Momentum is not conserved in both the horizontal and vertical direction.

A.

(1) only

B.

(2) only

C.

(3) only

D.

(2) and (3) only

107 In a baseball game, the catcher caught a 3 g ball of velocity 10 m s−1. The impact time of the ball and the glove is 0.1 second. Find the force acting on the catcher. A.

0.3 N

B.

0.4 N

C.

0.6 N

D.

0.9 N

108 A machine gun can fire out bullets at a rate of 80 bullets per minute.Eeach bullet is 4 g and the fire out speed is 450 m s−1. The gun is fired on a wall and all momentum of the bullets is transferred to the wall. Find the average force on the wall acted by the bullets. A.

2.9 N

B.

2.4 N

C.

2.0 N

D.

1.5 N

109 Which of the followings cases is/are possible? (1)

A stationary mass explodes into two identical parts. One of them moves with 2 units of speed and another is stationary.

(2)

A stationary mass explodes into three identical parts. The final total momentum of all three parts is zero.

(3)

A moving mass explodes into two identical parts. Both of them are stationary after explosion.

A.

(1) only

B.

(2) only

C.

(3) only

D.

(1), (2) and (3)

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110 A small mass moves with uniform speed hits a wall elastically and rebounds along its original path. Which of the following momentum-time graphs correctly describes the motion of the ball? A.

B.

C.

D.

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111 A ball is released from rest at a certain height. Which of the following momentum-time graphs correctly describe the motion of the ball from the time it is released to the time just before it hits the ground? (Take the downward direction as positive.) A.

B.

C.

D.

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112 A small mass moving at uniform speed hits a massive wall inelastically; it bounces back along its original path. Which of the following kinetic energy-time graphs correctly describe the motion of the mass? A.

B.

C.

D.

113 Block A of 5 kg is moving towards right on a frictionless surface at 2 m s−1. Suddenly it hits another identical block B, which is moving towards right at 1 m s−1. Find the kinetic energy of B if the velocity of A is 1 m s−1 after the collision. A.

10 J

B.

20 J

C.

15 J

D.

25 J

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114 Which of the following is/are CORRECT for an elastic collision? (1)

Two identical masses are moving towards each other at the same speed and are having a head on collision. After collision, the two masses will become stationary according to the conservation of momentum.

(2)

Two identical masses A and B, A is moving with uniform velocity u and B is stationary. After the collision, A will become stationary while B will move with uniform velocity u because of the conservation of momentum.

(3)

Two identical masses A and B, A is moving with uniform velocity u and B is moving with 0.5 u. After the collision, A moves with 2u and B moves with –0.5 u because of conservation of momentum.

A.

(1) only

B.

(2) only

C.

(1) and (3) only

D.

(1) and (2) only

115 In a snooker game, a 5 g white ball of speed 0.7 m s−1 hits the border of the table as shown in the following figure. Find the x-component of the momentum of the white ball after the elastic collision.

A.

0.30 kg m s−1

B.

0.82 kg m s−1

C.

1.0 kg m s−1

D.

0.49 kg m s−1

116 In a snooker game, a 5 g white ball of speed 0.7 m s−1 hits the border of the table as shown in the following figure. Find the change in the y-component of the momentum of the white ball before and after the elastic collision.

A.

0.56 kg m s−1

B.

1.77 kg m s−1

C.

2.5 kg m s−1

D.

0.99 kg m s−1

117 Find the momentum change of the ball in the following figure if the collision is elastic and the wall is extremely massive.

A.

0 kg m s−1

B.

2 kg m s−1

C.

4 kg m s−1

D.

Not enough information, so it cannot be determined. End (02)Mechanics Revision MC Test.doc

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Mechanics Revision MC Test Answer

(02)Mechanics Revision MC Test.doc

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