Queens College, CUNY - PHYSICS 152

Chapter 4—The Laws of Motion

MULTIPLE CHOICE

1)Which of the following is not a fundamental force?

1. 1. the gravitational force
   2. the electromagnetic force
   3. the strong force
   4. the force of forward motion also known as the inertial force
   5. Choose this answer if two of the named forces are not fundamental.

2. Two forces are the only forces acting on a 3.0-kg object which moves with an acceleration of 3.0 m/s² in the positive y direction. If one of the forces acts in the positive x direction and has a magnitude of

8.0 N, what is the magnitude of the other force?

1. 12 N
2. 14 N
3. 16 N
4. 18 N
5. 22 N

3. The horizontal surface on which the block slides is frictionless. If F = 20 N and M = 5.0 kg, what is the magnitude of the resulting acceleration of the block?

a.   5.3 m/s²

b.   6.2 m/s²

c.   7.5 m/s²

d.   4.7 m/s²

e.   3.2 m/s²

4. The only two forces acting on a body have magnitudes of 20 N and 35 N and directions that differ by 80?. The resulting acceleration has a magnitude of 20 m/s². What is the mass of the body?
   1. 2.4 kg
   2. 2.2 kg
   3. 2.7 kg
   4. 3.1 kg
   5. 1.5 kg

5. 

   

   If the only forces acting on a 2.0-kg mass are                N and                      N, what is the magnitude of the acceleration of the particle?

6. 

   

   At an instant when a 4.0-kg object has an acceleration equal to    m/s², one of the two forces

acting on the object is known to be             N. Determine the magnitude of the other force acting on the object.

1. 1. 2.0 N
   2. 13 N
   3. 18 N
   4. 1.7 N
   5. 20 N

7. 

   

   A 1.5-kg object has a velocity of 5 m/s at t = 0. It is accelerated at a constant rate for five seconds

1. 1. 3.8 N
   2. 3.2 N
   3. 2.8 N
   4. 4.3 N
   5. 4.6 N

8. 

   

   A 1.5-kg object has a velocity of 5 m/s at t = 0. It is accelerated at a constant rate for five seconds

a.   65?

b.    56?

c.   61?

d.    49?

e.   27?

9. 

   

   

   A 2.0-kg object has a velocity of 4.0 m/s at t = 0. A constant resultant force of (2.0 + 4.0 ) N then acts on the object for 3.0 s. What is the magnitude of the object's velocity at the end of the 3.0-s interval?
   1. 9.2 m/s
   2. 6.3 m/s
   3. 8.2 m/s
   4. 7.2 m/s
   5. 7.7 m/s

10. 

    

    

    A 1.5-kg mass has an acceleration of (4.0 ? 3.0 ) m/s². Only two forces act on the mass. If one of the

1. 1. 4.1 N
   2. 6.1 N
   3. 5.1 N
   4. 7.1 N
   5. 2.4 N

11. Only two forces act on a 3.0-kg mass. One of the forces is 9.0 N east, and the other is 8.0 N in the direction of 62? north of west. What is the magnitude of the acceleration of the mass?

a.   2.0 m/s²

b.   2.4 m/s²

c.   3.3 m/s²

d.   2.9 m/s²

e.   5.7 m/s²

12. A bumper car is moving at constant velocity when another bumper car starts to push on it with a constant force at an angle of 60 degrees with respect to the first car's initial velocity. The second bumper car continues pushing in exactly that direction for some time. What is most likely to happen is that
    1. the first car will stop moving.
    2. the first car will move in the direction of the force.
    3. the first car's velocity will increase in magnitude but not change direction.
    4. the first car's velocity will gradually change direction more and more toward that of the force while increasing in magnitude.
    5. the first car's velocity will gradually change direction more and more toward that of the force while decreasing in magnitude.

13. You have a machine which can accelerate pucks on frictionless ice. Starting from rest, the puck travels a distance x in time t when force F is applied. If force 3F is applied, the distance the puck travels in time t is
    1. x.

b. (3/2)x.

c.   3x.

d. (9/2)x.

e.   9x.

14. 

    A constant force F is applied to a body of mass m that initially is headed east at velocity v₀ until its velocity becomes ?v₀. The total time of travel is 2t. The total distance the body travels in that time is a.

.

.

.

.

.

15. Two experiments are performed. In (A), an 18.0 N force pushes horizontally on a 2.00 kg block that then pushes on a 4.00 kg block. In (B), an 18.0 N force pushes on a 4.00 kg block that then pushes on a

2.00 kg block. Which statement is correct?

1. The acceleration is 3.00 m/s² in both (A) and (B).
2. The acceleration is 4.50 m/s² in both (A) and (B).
3. The acceleration is 6.00 m/s² in both (A) and (B).
4. The acceleration is 9.00 m/s² in both (A) and (B).
5. The 2.00 kg block has a 9.00 m/s² acceleration. The 4.00 kg block has a 4.50 m/s² acceleration.

16. A juggler throws two balls up to the same height so that they pass each other halfway up when A is rising and B is descending. Ignore air resistance and buoyant forces. Which statement is true of the two balls at that point?
    1. There is an residual upward force from the hand on each ball.
    2. There is a greater residual force from the hand on A than there is on B.
    3. Only gravity acts on B but there is an additional residual force from the hand on A.
    4. There is an additional downwards force besides gravity on each ball.
    5. The only force acting on each ball is the gravitational force.     
17. A book is placed on a chair. Then a videocassette is placed on the book. The floor exerts a normal force
    1. on all three.
    2. only on the book.
    3. only on the chair.
    4. upwards on the chair and downwards on the book.
    5. only on the objects that you have defined to be part of the system.     
18. A chair is placed on a rug. Then a book is placed on the chair. The floor exerts a normal force
    1. on all three.
    2. only on the book.
    3. only on the rug.
    4. upwards on the rug and downwards on the chair.
    5. only on the objects you have defined to be part of the system.     
19. A book is placed on a chair. Then a videocassette is placed on the book. The floor exerts a normal force
    1. on all three.
    2. only on the book.
    3. only on the chair.

19. 4. upwards on the chair and downwards on the book.
    5. only on the objects that you have defined to be part of the system.     
20. Two bodies, A and B, collide as shown in Figures I and II below.

Which statement is true?

1. 1. They exert equal and opposite forces on each other in I but not in II.
   2. They exert equal and opposite force on each other in II but not in I.
   3. They exert equal and opposite force on each other in both I and II.
   4. The forces are equal and opposite to each other in I, but only the components of the forces parallel to the velocities are equal in II.
   5. The forces are equal and opposite in I, but only the components of the forces perpendicular to the velocities are equal in II

21. You throw a ball up in the air and hold your hand under it to catch it when it comes down. The reason why the ball stops is because
    1. your hand is there: your hand exerts no force on the ball.
    2. your hand exerts a force on the ball perpendicular to its velocity.
    3. your hand exerts a force on the ball in the direction of its velocity.
    4. your hand exerts a force on the ball in the direction opposite to its velocity.
    5. your hand and the ball exert forces in the same direction on each other.
22. You hold a tennis racket in your hand. On top of the racket you have balanced a ball. Which statement is true?
    1. The force of your hand on the racket and the force of the ball on the racket are equal and opposite.
    2. The force of the racket on your hand and the force of the ball on the racket are equal and opposite.
    3. The force of your hand on the racket and the force of the racket on the ball are equal and opposite.
    4. The force of the racket on your hand and the force of the racket on the ball are equal and opposite.
    5. The force of your hand on the racket and the force of the racket on your hand are equal and opposite.

23. In order to jump off the floor, the floor must exert a force on you
    1. in the direction of and equal to your weight.
    2. opposite to and equal to your weight.
    3. in the direction of and less than your weight.
    4. opposite to and less than your weight.
    5. opposite to and greater than your weight.

24. When an acrobat hangs motionless from a pair of rings
    1. she has no measurable weight.
    2. her weight depends on the angles the ropes make with the ceiling.
    3. her weight is reduced by the upward force the rings exert on her.
    4. her weight is increased by the upward force the rings exert on her.
    5. she exerts a gravitational force on the Earth that is equal to the sum of the forces the rings exert on her.

25. A catcher arranges to catch a baseball dropped from a height 50 m above his glove. However, his friends substitute a soft 250 g red grapefruit, so that it will smash apart when he catches it. His glove stops the grapefruit in 0.010 s. What force does the glove exert on the grapefruit?

a.   0.078 3 N

b. 783 N

c.   2 450 N

d.   24 500 N

e.   78 300 N

26. Which type of force would be the equal and opposite force to a gravitational force?
    1. gravitational
    2. electromagnetic
    3. strong
    4. weak
    5. It could be any one of the above or some combination of them.     
27. A book is resting on a table. How many forces would be in the free-body diagram of the book?
    1. one
    2. two of the same type
    3. two of different types
    4. three or more of the same type
    5. three or more of at least two different types

28. In the figure, if the tension in string 1 is 34 N and the tension in string 2 is 24 N, what is the mass of the object shown?

1. 1. 7.3 kg
   2. 5.5 kg
   3. 1.8 kg
   4. 3.7 kg
   5. 4.5 kg

29. If M = 2.0 kg, what is the tension in string 1?

1. 1. 1.2 N
   2. 11 N
   3. 34 N
   4. 3.5 N
   5. 40 N

30. If M = 6.0 kg, what is the tension in string 1?

1. 1. 39 N
   2. 34 N
   3. 29 N
   4. 44 N
   5. 51 N

31. If M = 1.1 kg, what is the tension in string 1?

1. 1. 54 N
   2. 47 N
   3. 40 N
   4. 62 N
   5. 57 N

32. An object of unknown weight is suspended as shown. The tension in rope 1 is 25 lb, and the tension in rope 2 is 31 lb. What is the weight of the suspended object?

1. 1. 36 lb
   2. 33 lb
   3. 41 lb
   4. 39 lb
   5. 56 lb

33. If ? = 40?, ? = 60?, and M = 4.0 kg, determine the tension in string 1.

1. 1. 15 N

34. If ? = 40? and the tension in string 2 is 30 N, determine M.

1. 1. 3.4 kg
   2. 3.6 kg
   3. 2.6 kg
   4. 4.9 kg
   5. 7.5 kg

35. A uniform ladder 15 ft long is leaning against a frictionless wall at an angle of 53? above the horizontal. The weight of the ladder is 30 pounds. A 75-lb boy climbs 6.0-ft up the ladder. What is the magnitude of the friction force exerted on the ladder by the floor?
    1. 43 lb
    2. 34 lb
    3. 38 lb
    4. 47 lb
    5. 24 lb

36. A horizontal uniform meter stick supported at the 50-cm mark has a mass of 0.50 kg hanging from it at the 20-cm mark and a 0.30 kg mass hanging from it at the 60-cm mark. Determine the position on the meter stick at which one would hang a third mass of 0.60 kg to keep the meter stick balanced.
    1. 74 cm
    2. 70 cm
    3. 65 cm
    4. 86 cm
    5. 62 cm

37. The figure shows a uniform, horizontal beam (length = 10 m, mass = 25 kg) that is pivoted at the wall, with its far end supported by a cable that makes an angle of 51? with the horizontal. If a person (mass

= 60 kg) stands 3.0 m from the pivot, what is the tension in the cable?

1. 1. 0.83 kN
   2. 0.30 kN
   3. 0.38 kN
   4. 0.42 kN
   5. 3.0 kN

38. A uniform 100-lb beam is held in a vertical position by a pin at its lower end and a cable at its upper end. A horizontal force (magnitude P) acts as shown in the figure. If P = 75 lb, what is the tension in the cable?

1. 1. 54 lb
   2. 69 lb
   3. 47 lb
   4. 61 lb
   5. 75 lb

39. A 25-ft long crane supported at its lower end by a pin is elevated by a horizontal cable as shown in the figure. A 250-lb load is suspended from the outer end of the crane. The center of gravity of the crane is 10 ft from the pin, and the crane weighs 200 lb. What is the tension in the horizontal cable?

1. 1. 610 lb
   2. 540 lb
   3. 640 lb
   4. 570 lb
   5. 2 000 lb

40. A uniform beam having a mass of 60 kg and a length of 2.8 m is held in place at its lower end by a pin. Its upper end leans against a vertical frictionless wall as shown in the figure. What is the magnitude of the force the pin exerts on the beam?

1. 1. 0.68 kN
   2. 0.57 kN
   3. 0.74 kN
   4. 0.63 kN
   5. 0.35 kN

41. A uniform 120-lb beam is supported in a horizontal position by a pin and cable as shown in the figure. What is the magnitude of the force by the pin on the beam?

1. 1. 94 lb
   2. 88 lb
   3. 63 lb
   4. 75 lb
   5. 150 lb

42. The diagrams below show forces applied to a wheel that weighs 20 N. The symbol W stands for the weight. In which diagram(s) is(are) the wheel in equilibrium?

1. 1. A
   2. B
   3. C
   4. D
   5. A and C

43. The diagrams below show forces of magnitude F applied to an equilateral triangular block of uniform thickness. In which diagram(s) is(are) the block in equilibrium?

1. 1. A
   2. B

1. 3. C
   4. D
   5. A and B

44. An object of mass m is suspended by two coplanar wires, as shown below. The tension in each wire has a magnitude given by

.

.

.

d. mg.

e.  

45. If F = 4.0 N and m = 2.0 kg, what is the magnitude a of the acceleration for the block shown below? The surface is frictionless.

a.   5.3 m/s²

b.   4.4 m/s²

c.   3.5 m/s²

d.   6.2 m/s²

e.   8.4 m/s²

46. A block is pushed up a frictionless 30? incline by an applied force as shown. If F = 25 N and M = 3.0 kg, what is the magnitude of the resulting acceleration of the block?

47. A 5.0-kg object is suspended by a string from the ceiling of an elevator that is accelerating downward at a rate of 2.6 m/s². What is the tension in the string?
    1. 49 N
    2. 36 N
    3. 62 N
    4. 13 N
    5. 52 N

48. The tension in a string from which a 4.0-kg object is suspended in an elevator is equal to 44 N. What is the acceleration of the elevator?
    1. 11 m/s² upward
    2. 1.2 m/s² upward
    3. 1.2 m/s² downward
    4. 10 m/s² upward
    5. 2.4 m/s² downward

49. A 5.0-kg mass is attached to the ceiling of an elevator by a rope whose mass is negligible. What force does the mass exert on the rope when the elevator has an acceleration of 4.0 m/s² upward?
    1. 69 N downward
    2. 29 N downward
    3. 49 N downward
    4. 20 N downward
    5. 19 N downward

50. A 5.0-kg mass is suspended by a string from the ceiling of an elevator that is moving upward with a speed which is decreasing at a constant rate of 2.0 m/s in each second. What is the tension in the string supporting the mass?
    1. 49 N
    2. 39 N
    3. 59 N
    4. 10 N
    5. 42 N

51. A person weighing 0.70 kN rides in an elevator that has an upward acceleration of 1.5 m/s². What is the magnitude of the force of the elevator floor on the person?
    1. 0.11 kN
    2. 0.81 kN
    3. 0.70 kN

1. 4. 0.59 kN
   5. 0.64 kN

52. A 3.0-kg block slides on a frictionless 20? inclined plane. A force of 16 N acting parallel to the incline and up the incline is applied to the block. What is the acceleration of the block?
    1. 2.0 m/s² down the incline
    2. 5.3 m/s² up the incline
    3. 2.0 m/s² up the incline
    4. 3.9 m/s² down the incline
    5. 3.9 m/s² up the incline

53. A 2.0-kg block slides on a frictionless 25? inclined plane. A force of 4.6 N acting parallel to the incline and up the incline is applied to the block. What is the acceleration of the block?
    1. 1.8 m/s² up the incline
    2. 2.3 m/s² up the incline
    3. 6.6 m/s² down the incline
    4. 1.8 m/s² down the incline
    5. 2.3 m/s² down the incline

54. A 2.0-kg block slides on a frictionless 15? inclined plane. A force acting parallel to the incline is applied to the block. The acceleration of the block is 1.5 m/s² down the incline. What is the applied force?
    1. 8.1 N down the incline
    2. 3.0 N down the incline
    3. 2.1 N up the incline
    4. 3.0 N up the incline
    5. 8.1 N up the incline

55. The apparent weight of a fish in an elevator is greatest when the elevator
    1. moves downward at constant velocity.
    2. moves upward at constant velocity.
    3. accelerates downward.
    4. accelerates upward.
    5. is not moving.

56. The vector sum of three co-planar forces
    1. must be zero.
    2. must be perpendicular to one of the three.
    3. must be parallel to one of the three.
    4. must be perpendicular to the plane.
    5. may have any direction in the plane.

57. 

    

    

    

    

    

    When the vector sum of three co-planar forces, ,        and                  , is parallel to           , we can conclude that and
    1. must sum to zero.
    2. must be equal and opposite.

    3. 

       must have equal and opposite components perpendicular to     .

    4. 

       must have equal and opposite components parallel to    .

    5. 

       must have equal and opposite components parallel and perpendicular to     .                          
58. A constant force is applied to a body that is already moving. The force is directed at an angle of 60 degrees to the direction of the body's velocity. What is most likely to happen is that
    1. the body will stop moving.
    2. the body will move in the direction of the force.
    3. the body's velocity will increase in magnitude but not change direction.
    4. the body will gradually change direction more and more toward that of the force while speeding up.
    5. the body will first stop moving and then move in the direction of the force.
59. The first of two identical boxes of mass m is sitting on level ground. The second box is sitting on a ramp that makes a 20? angle with the ground. The normal force of the level ground on the first box is N_L; the normal force of the ramp on the second box is N_R. Which statement is correct?
    1. N_R = N_L = mg.
    2. N_L = mg; N_R = mg sin 20?.
    3. N_L = mg; N_R = mg cos 20?.
    4. N_L = mg; N_R = ?mg cos 20?.
    5. N_R = ?N_L = ?mg.

60. A heavy weight is supported by two cables that exert tensions of magnitude T₁ and T₂. Which statement is correct?

1. 1. T₁ = T₂.
   2. T_1y = T_2y.
   3. T₁ > T₂.
   4. T₁ < T₂.
   5. We need the mass of the box in order to determine the correct answer.                    

61. 

    

    Two people, each of 70 kg mass, are riding in an elevator. One is standing on the floor. The other is hanging on a rope suspended from the ceiling. Compare the force            the floor exerts on the first

person to the force   the rope exerts on the second person. Which statement is correct?

1. 1. They are equal and opposite in direction.
   2. They are equal and have the same direction.

c.  

d.  

e.  

62. 

    

    Two people, each of 70 kg mass, are riding in an elevator. One is standing on the floor. The other is hanging on a rope suspended from the ceiling. Compare the acceleration         of the first person to the acceleration                                                                       of the second person. Which statement is correct?
    1. They are equal and opposite in direction.
    2. They are equal and have the same direction.

    3. 

       

       The acceleration   is greater than  , but they have the same direction.

    4. 

       

       The acceleration   is greater than  , but they have opposite directions.

    5. 

       

       The acceleration                         is less than , but they have the same direction.                  PTS:   1                     DIF:    Easy
63. The horizontal surface on which the objects slide is frictionless. If M = 2.0 kg, the tension in string 1 is 12 N. Determine F.

1. 1. 25 N
   2. 20 N
   3. 30 N
   4. 35 N
   5. 40 N

64. The horizontal surface on which the objects slide is frictionless. If F = 12 N, what is the tension in string 1?

1. 1. 35 N
   2. 30 N

1. 3. 40 N
   4. 45 N
   5. 25 N

65. The surface of the inclined plane shown is frictionless. If F = 30 N, what is the magnitude of the force exerted on the 3.0-kg block by the 2.0-kg block?

1. 1. 18 N
   2. 27 N
   3. 24 N
   4. 21 N
   5. 15 N

66. If P = 6.0 N, what is the magnitude of the force exerted on block 1 by block 2?

1. 1. 6.4 N
   2. 5.6 N
   3. 4.8 N
   4. 7.2 N
   5. 8.4 N

67. If F = 5.0 N, what is the magnitude of the force exerted by block 2 on block 1?

1. 1. 17 N

68. An astronaut who weighs 800 N on the surface of the earth lifts off from planet Zuton in a space ship. The free-fall acceleration on Zuton is 3.0 m/s² (down). At the moment of liftoff the acceleration of the space ship is 0.50 m/s² (up). What is the magnitude of the force of the space ship on the astronaut?
    1. 41 N
    2. 0.29 kN
    3. 0.24 kN
    4. 0.20 kN
    5. 0.37 kN

69. The horizontal surface on which the objects slide is frictionless. If M = 1.0 kg and the magnitude of the force of the small block on the large block is 5.2 N, determine F.

1. 1. 6.0 N
   2. 9.0 N
   3. 7.8 N
   4. 4.8 N
   5. 4.1 N

70. The horizontal surface on which the objects slide is frictionless. If F = 6.0 N and M = 1.0 kg, what is the magnitude of the force exerted on the large block by the small block?

1. 1. 7.7 N
   2. 9.8 N
   3. 9.1 N
   4. 8.4 N
   5. 6.5 N

71. A 6.0-kg object is suspended by a vertical string from the ceiling of an elevator which is accelerating upward at a rate of 1.8 m/s². Determine the tension in the string.
    1. 11 N

72. An 8.0-kg object rests on the floor of an elevator which is accelerating downward at a rate of 1.3 m/s². What is the magnitude of the force the object exerts on the floor of the elevator?
    1. 59 N
    2. 10 N
    3. 89 N
    4. 68 N
    5. 78 N

73. A 70-kg stunt artist rides in a rocket sled which slides along a flat inclined surface. At an instant when the sled's acceleration has a horizontal component of 6.0 m/s² and a downward component of 2.8 m/s², what is the magnitude of the force on the rider by the sled?
    1. 0.83 kN
    2. 0.98 kN
    3. 0.65 kN
    4. 0.68 kN
    5. 0.72 kN

74. If F = 40 N and M = 1.5 kg, what is the tension in the string connecting M and 2M? Assume that all surfaces are frictionless.

75. The system shown is released from rest and moves 50 cm in 1.0 s. What is the value of M? All surfaces are frictionless.

1. 1. 0.42 kg
   2. 0.34 kg
   3. 0.50 kg
   4. 0.59 kg
   5. 0.68 kg

76. If F = 40 N and M = 2.0 kg, what is the magnitude of the acceleration of the suspended object? All surfaces are frictionless.

a.   1.2 m/s²

b.   2.0 m/s²

c.   1.5 m/s²

d.   2.5 m/s²

e.   5.6 m/s²

77. If M = 2.2 kg, what is the tension in the connecting string? The pulley and all surfaces are frictionless.

1. 1. 6.4 N
   2. 5.9 N

78. A 5.0-kg mass sits on the floor of an elevator that has a downward acceleration of 1.0 m/s². On top of the 5.0-kg mass is an object of unknown mass. The force of the elevator on the 5.0-kg mass is 80 N up. Determine the unknown mass.
    1. 3.3 kg
    2. 2.4 kg
    3. 1.6 kg
    4. 4.1 kg
    5. 5.0 kg

79. If the tension, T, is 15 N and the magnitude of the acceleration, a, is 3.0 m/s², what is the mass, m, of the suspended object? Assume that all surfaces and the pulley are frictionless.

1. 1. 3.1 kg
   2. 2.5 kg
   3. 2.8 kg
   4. 2.2 kg
   5. 3.7 kg

80. If F = 8.0 N and M = 1.0 kg, what is the tension in the connecting string? The pulley and all surfaces are frictionless.

81. In the figure, if F = 2.0 N and M = 1.0 kg, what is the tension in the connecting string? The pulley and all surfaces are frictionless.

1. 1. 2.6 N
   2. 1.1 N
   3. 2.1 N
   4. 1.6 N
   5. 3.7 N

82. A 3.0-kg block moves up a 40? incline with constant speed under the action of a 26-N force acting up and parallel to the incline. What magnitude force must act up and parallel to the incline for the block to move down the incline at constant velocity?
    1. 14 N
    2. 12 N
    3. 16 N
    4. 18 N
    5. 25 N

83. A box rests on the (horizontal) back of a truck. The coefficient of static friction between the box and the surface on which it rests is 0.24. What maximum distance can the truck travel (starting from rest and moving horizontally with constant acceleration) in 3.0 s without having the box slide?
    1. 14 m
    2. 11 m
    3. 19 m
    4. 24 m
    5. 29 m

84. The three blocks shown are released from rest and are observed to move with accelerations that have a magnitude of 1.5 m/s². What is the magnitude of the friction force on the block that slides horizontally? Disregard any pulley mass or friction in the pulley and let M = 2.0 kg.

1. 1. 6.0 N
   2. 5.1 N
   3. 5.5 N
   4. 4.6 N
   5. 3.7 N

85. Two identical springs with spring constant 50 N/m support a 5.0 N weight as in the picture below. What is the tension in spring A?

a.   1.45 N

b.   2.50 N

c.   2.89 N

d.   3.75 N

e.   5.00 N

86. When you drag a toy teddy bear along the floor by a force that is parallel to the floor, the magnitude of the force of friction
    1. is independent of velocity or acceleration.
    2. increases when the velocity increases.
    3. is proportional to the acceleration.
    4. decreases when the force parallel to the floor increases.
    5. increases when the force parallel to the floor increases.     
87. Three boxes slide on a frictionless horizontal surface when pulled by a force of magnitude F. When we compare the tensions T₁ and T₂ with the force F, we find that

1. 1. T₁ = T₂ = F.
   2. T₁ = F > T₂.
   3. F > T₁ = T₂.
   4. F > T₁ > T₂.

e.    F ? T₁ < T₁ ? T₂.

88. Three boxes are pushed across a frictionless horizontal surface as shown. When we compare the normal force N_2,5 that mass 2m exerts on mass 5m with the normal force N_5,10 that mass 5m exerts on mass 10m, we find that

a.   N_2,5 = N_5,10 = F.

b.   N_2,5 = F > N_5,10.

c.   F > N_2,5 = N_5,10.

d.   F > N_2,5 > N_5,10.

e.   F > N_5,10 > N_2,5.

89. Given the equation                                                         , which answer or answers provide(s) the best description of a possible physical situation?
    1. A 20.00 N tension pulls a 2.00 kg mass. The 2.00 kg mass pulls another 2.00 kg mass.
    2. A 20.00 N force pushes a 2.00 kg mass. The 2.00 kg mass pushes another 2.00 kg mass.
    3. A 2.00 kg mass on a flat surface is acted on by gravity while another 2.00 kg mass sits on top of it.
    4. All of the situations above are possible.
    5. Only (a) and (b) above are possible.

90. Given the equation                                                                                           , which answer

provides the best description of a possible physical situation?

1. 1. A 3.00 kg mass is suspended from the ceiling.
   2. A 2.00 kg mass hanging over a pulley drags a 3.00 kg mass along a frictionless horizontal surface.
   3. A 3.00 kg mass hanging over a pulley drags a 2.00 kg mass along a frictionless horizontal surface.
   4. A 3.00 kg mass hanging over a pulley drags a 5.00 kg mass along a frictionless horizontal

surface.

1. 5. A 5.00 kg mass hanging over a pulley drags a 3.00 kg mass along a frictionless horizontal surface.

NARRBEGIN: Exhibit 05-01

Exhibit 5-1

Use this exhibit to answer the following question(s). NARREND

91. Refer to Exhibit 5-1. A hand exerts an upward force of 6.70 N on the 1.70 kg mass. The magnitudes of the tensions are

a.   T₁ = 15.8 N; T₂ = 10.0 N.

b.   T₁ = 15.8 N; T₂ = 16.7 N.

c.   T₁ = 22.5 N; T₂ = 10.0 N.

d.   T₁ = 22.5 N; T₂ = 16.7 N.

e.   T₁ = 32.5 N; T₂ = 10.0 N.

92. Refer to Exhibit 5-1. The string supporting the 1.70 kg mass is cut. The magnitudes of the tension in string 1 before and after string 2 is cut are

a.   T_1,i = 22.5 N; T_1,f = 5.80 N.

b.   T_1,i = 39.2 N; T_1,f = 5.80 N.

c.   T_1,i = 22.5 N; T_1,f = 22.5 N.

d.   T_1,i = 39.2 N; T_1,f = 22.5 N.

e.   T_1,i = 39.2 N; T_1,f = 39.2 N.

93. A 6.00 kg block is placed on a 30.0? incline and connected to another block on a 36.87? incline. Although the surfaces are frictionless the blocks do not move. What is the mass in kilograms of the block on the 36.87? incline?

a.   1.80

b.   3.00

c.   4.00

d.   5.00

e.   6.00

NARRBEGIN: Exhibit 05-02

Exhibit 5-2

Use this exhibit to answer the following question(s). NARREND

94. 

    

    Refer to Exhibit 5-2. When the elevator accelerates upwards with an acceleration of 2.20 m/s², the magnitudes of          and    are

a.   30.4 N; 15.2 N.

b.   39.2 N; 19.6 N.

c.   45.6 N; 15.2 N.

d.   48.0 N; 24.0 N.

e.   72.0 N; 24.0 N.

95. 

    

    Refer to Exhibit 5-2. When the elevator accelerates downwards with an acceleration of 2.20 m/s², the magnitudes of          and    are

a.   30.4 N; 15.2 N.

b.   39.2 N; 19.6 N.

c.   45.6 N; 15.2 N.

d.   48.0 N; 24.0 N.

e.   72.0 N; 24.0 N.

96. Aline and Charlie are arguing as to whether or not it is possible in principle for an elevator to have an acceleration of magnitude greater than g. In the course of their discussion they come up with the statements below. Which one is correct?
    1. No, because once

       

          reaches g, the elevator is in free fall.
    2. No, because an acceleration greater than g is not possible.
    3. Yes, because it can reach an acceleration greater than g when the cable breaks.
    4. Yes, because it can reach an acceleration greater than g if the motor is strong enough.
    5. No, because it cannot exceed its terminal acceleration.

PROBLEM