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**Multiple Choice Practice **

1) In a collision between a huge SUV and a small hybrid car, the SUV exerts a larger force on the hybrid than the hybrid exerts on the SUV.

A) True

B) False

C) It depends on whether the collision is a head-on collision or a rear-end collision.

2) A box is placed on a table which rests on the floor. The box pushes on the table; the reaction force to the box's push on the table is the table's push on the floor.

A) True

A) True

B) False

3) In order to get an object moving, you must push harder on it than it pushes back on you.

B) False

5) If you pound a feather with a hammer, which one feels a greater force?

A) always the feather

B) always the hammer

C) The size of the force is always exactly the same on both of them.

D) If the feather moves, then it felt the greater force. Otherwise the force was the same on both.

10) You are in a train traveling on a horizontal track and notice that a piece of luggage starts to slide directly toward the front of the train. From this observation, you can conclude that this train is

A) speeding up.

B) slowing down.

D) speeding up and changing direction.

E) slowing down and changing direction.

C) changing direction.

11) While flying horizontally in an airplane, you notice that a string dangling from the overhead luggage compartment hangs at rest at 15° away from the vertical toward the front of the plane. Using this observation, you can conclude that the airplane is

A) moving forward.

B) moving backward.

C) accelerating forward.

D) accelerating backward.

E) not accelerating because the string is at rest.

12) An elevator suspended by a vertical cable is moving downward but slowing down. The tension in the cable must be

A) greater than the weight of the elevator.

B) less than than the weight of the elevator.

A) down the ramp.

B) up the ramp.

C) perpendicular to the ramp.

C) equal to the weight of the elevator.

13) A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point

D) vertically downward.

E) None of the above choices is correct.

14) A bucket is being lowered by a very light rope with a constant downward velocity. The tension in the rope must be

A) equal to the weight of the bucket. C) less than the weight of the bucket.

B) greater than the weight of the bucket.

**Multiple Choice Practice **

16) You push on box G that is next to box H, causing both boxes to slide along the floor, as shown in the figure.

The reaction force to your push is

A) the push of box G on box H.

B) the push of box H on box G.

D) the upward force of the floor n box G.

E) the acceleration of box G.

C) the push of box G against you.

18) An object is moving with constant non-zero velocity. Which of the following statements about it must be true?

A) A constant force is being applied to it in the direction of motion.

B) A constant force is being applied to it in the direction opposite of motion.

C) A constant force is being applied to it perpendicular to the direction of motion.

D) The net force on the object is zero.

E) Its acceleration is in the same direction as it velocity.

25) An object of mass m rests on a flat table. The earth pulls on this object with a force of magnitude mg . What is the reaction force to this pull?

A) The table pushing up on the object with force mg .

B) The object pushing down on the table with force mg .

C) The table pushing down on the floor with force mg .

D) The object pulling upward on the Earth with force mg .

E) The table pulling upward on the Earth with force mg .

33) When a 45-kg person steps on a scale in an elevator, the scale reads a steady 480 N. Which of the following statements must be true? (There could be more than one correct choice.)

A) The elevator is accelerating upward at a constant rate.

B) The elevator is accelerating downward at a constant rate.

C) The elevator is moving upward at a constant rate.

D) The elevator is moving downward at a constant rate.

E) From the given information, we cannot tell if the elevator is moving up or down.

34) When a 45-kg person steps on a scale in an elevator, the scale reads a steady 410 N. Which of the following statements must be true? (There could be more than one correct choice.)

A) The elevator is accelerating upward at a constant rate.

B) The elevator is accelerating downward at a constant rate.

C) The elevator is moving upward at a constant rate.

D) The elevator is moving downward at a constant rate.

E) From the given information, we cannot tell if the elevator is moving up or down.

**Multiple Choice Practice **

35) Inside of a train a ball of weight W is hanging by a light wire at rest from the ceiling. The wire makes an angle

*θ*

with the ceiling, as shown in the figure. Which one of the following conditions must be true about the tension T in the wire?

*A) T sin θ = W *

*B) T cos θ = W *

*C) T tan θ = W *

D)

E)

*T = W *

*T = ma *

36) In the figure, a 10-lb weight is suspended from two spring scales, each of which has negligible weight.

Which one of the following statements about the readings in the scales is true?

A) Each scale will read 5 lb.

B) The top scale will read zero, the lower scale will read 10 lb.

C) The lower scale will read zero, the top scale will read 10 lb.

D) Each scale will show a reading between one and 10 lb, such that the sum of the two is 10 lb. However, exact readings cannot be determined without more information.

E) None of these is true.

37) Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to the right, and both weigh the same.

Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the upper block, A?

A) D)

B)

E)

C)

**Multiple Choice Practice **

38) Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to the right, and both weigh the same.

Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the lower block, B?

A)

D)

B)

E) None of these diagrams is correct.

C)

39) As shown in the figure, a woman is straining to lift a large crate, but without success because it is too heavy.

We denote the forces on the crate as follows: P is the magnitude of the upward force being exerted on the crate by the person, C is the magnitude of the vertical contact force on the crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

*A) P + C = W *

*B) P + C < W *

C)

D)

*P + C > W *

*P = C *

40) A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle

θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to

A) W .

*B) W + P. *

*C) W + P cos θ. *

D) W + P sin θ.

*E) W - P sin θ. *

**Multiple Choice Practice **

41) A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle

θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The friction force on the box due to the floor is equal to

*A) P sin θ *

*B) P cos θ *

C) 0

D)

E)

*P cos θ + W *

*P + W *

42) In the figure, what does the spring scale read? The pulleys are ideal and the strings and scale are also massless.

A) exactly 2.0 N.

B) exactly 1.0 N

D) 0.00 N

E) more than 19.6 N

C) 0.50 N

43) Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord. The mass of P is greater than that of Q. A horizontal force is applied to box Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P is

A) zero.

B) less than F but not zero.

C) equal to F .

D) greater than F .

44) Three boxes are pulled along a horizontal frictionless floor by a constant horizontal pull P . The boxes are connected by very light horizontal strings having tensions T 1 and T 2 as shown in the figure. Which of the following statements about the tensions is correct? (There could be more than one correct choice.)

*A) T 1 = P *

*B) T 2 = P *

D) T 2 > T 1

E) T 1 > T 2

*C) T 1 + T 2 = P *

45) Two boxes, A and B, are connected by a horizontal string S on a horizontal floor. A very light wire pulls horizontally on box B, as shown in the figure, with a force of 100 N. The reaction force to this pull is

A) the pull that box B exerts on string S.

B) the pull that string S exerts on box B.

C) the pull that string S exerts on box A.

D) the pull of box B on the wire.

E) the force that box A exerts on box B.

**Multiple Choice Practice **

46) Two boxes are connected to each other by a string as shown in the figure. The 10-N box slides without friction on the horizontal table surface. The pulley is ideal and the string has negligible mass. What is true about the tension T in the string?

A) T = 10 N

B) T = 20 N

C) T = 30 N

D)

E)

T < 30 N

T > 30 N

47) Two objects of unequal masses, M and m ( M > m ), are connected by a very light cord passing over an ideal pulley of negligible mass. When released, the system accelerates, and friction is negligible.

Which one of the following free-body diagrams most realistically represents the forces acting on the two objects in the moving system?

A) C)

D)

B)

**Multiple Choice Practice **

50) Two objects have masses m and 5 m , respectively. They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance. Which one of the following statements about these objects is correct?

A) It takes the lighter object 5 times longer to reach the bottom of the ramp than the heavier.

B) It takes the lighter object 10 times longer to reach the bottom of the ramp than the heavier.

C) It takes the heavier object 5 times longer to reach the bottom of the ramp than the lighter.

D) It takes the heavier object 10 times longer to reach the bottom of the ramp than the lighter.

E) The two objects reach the bottom of the ramp at exactly the same time.

51) A block of mass m sits at rest on a rough inclined ramp that makes an angle

*θ*

with the horizontal. What must be true about force of static friction f on the block?

*A) f > mg *

B) f > mg cos

*θ *

C) f > mg sin

*θ *

*D) f = mg cos θ *

E) f = mg sin

*θ *

52) A block of mass m sits at rest on a rough inclined ramp that makes an angle

*θ*

with the horizontal. What must be true about normal force F on the block due to the ramp?

*A) F > mg *

B) F > mg cos

*θ *

*C) F > mg sin θ *

D) F = mg cos

*θ *

E) F = mg sin

*θ *