physics

50. An astronaut on a strange planet has a mass of 80 kg and a weight of 240 N. What is the value of the acceleration due to gravity on this planet? A. 3 m/s2 B. 8 m/s2 C. 10 m/s2 D. 1/3 m/s2

A

6. What is the net force on an 900-kg airplane flying with a constant velocity of 180 km/hour north? A. zero B. 180 N C. 900 N D. 162,000 N

A

15. A woman pulls on one end of a rope, the other end of which is attached to a large box. The large box, however, does not move. The free-body diagram for the box should include A. a force by the rope B. a force by the woman C. both a force by the rope and a force by the woman D. neither a force by the rope nor a force by the woman

A

16. During a physics experiment, a fan is used to apply a push to a cart on a horizontal track. A student would like the net force on the cart to be 12 N to the right. The student knows that the friction force on the cart by the track will be 3 N to the left. The fan should exert a force of A. 15 N to the right B. 15 N to the left C. 9 N to the right D. 9 N to the left E. None of these

A

2. If there is no net force acting on an object, its motion will be one with ____ acceleration. A. zero B. a constant, non-zero C. an increasing D. a decreasing

A

22. A subway train is moving with constant velocity along a level section of track. The net force on the first subway car is ____ the net force on the last subway car. A. equal to B. much greater than C. slightly greater than D. less than

A

27. If the net force on an object is directed due west, which way does the acceleration point? A. due west B. due east C. west only if the velocity is west D. It could be in any westerly direction.

A

3. Assume that you are driving down a straight road at constant speed. A small ball is tied on the end of a string hanging from the rear view mirror. Which way will the ball swing when you apply the brakes? A. forward B. backward C. It will not swing.

A

35. You are applying a 400-N force to a freezer full of chocolate chip ice cream in an attempt to move it across the basement. It will not budge. The weight of the freezer (including the ice cream) is 1000 N. The friction force exerted by the floor on the freezer is A. 400 N. B. greater than 400 N but less than 1000 N. C. 1000 N. D. greater than 1000 N.

A

39. What net force is required to accelerate 20 kg at 5 m/s2. A. 100 N B. 25 N C. 15 N D. 4 N

A

40. What acceleration is produced by a force of 30 N acting on a mass of 10 kg? A. 3 m/s2 B. 10 m/s2 C. 30 m/s2 D. 300 m/s2

A

56. Two steel balls have the same size and shape, but one is hollow. They are dropped in air and their terminal speeds are measured. Which of the following statements is correct? A. The hollow ball has a smaller terminal speed because it requires a smaller air resistance to cancel the gravitational force on it. B. The hollow ball has a larger terminal speed because it requires a smaller air resistance to cancel the gravitational force on it. C. The terminal speeds are the same because the acceleration of gravity doesn't depend on mass. D. The terminal speeds are the same and equal to 10 m/s.

A

7. What is the net force on a 2000-kg car that is traveling in a straight line at a constant speed of 40 m/s? A. zero B. 40 N C. 2000 N D. (40 m/s) ´ (2000 kg)

A

71. In the physics world view, a force is exerted on one object by a second object. Taken together, the two forces that make up a Newton's third law force pair involve A. two objects B. three objects C. four objects

A

76. A child stands on a bathroom scale while riding in an elevator. The child's weight when the elevator is not moving is 500 N. What does the scale read when the elevator accelerates upward while traveling downward? A. greater than 500 N B. less than 500 N C. equal to 500 N

A

60. A 40-kg crate is being pushed across a horizontal floor by a horizontal force of 240 N. If the coefficient of sliding friction is 0.5, what is the acceleration of the crate? A. zero B. 1 m/s2 C. 3 m/s2 D. 6 m/s2

B

1. The property of an object at rest to remain at rest is known as A. inertness. B. inertia. C. resistance. D. sluggishness.

B

10. A small block sits on a horizontal table. In one experiment, a student pushes with a horizontal force of 5 N, but the block does not move. In a second experiment, the student pushes with a horizontal force of 8 N, but the block still does not move. The magnitude of the friction force exerted on the block is A. greater in the first experiment B. greater in the second experiment C. the same in the two experiments

B

13. In a tug-of-war, two teams pull in opposite directions on a large box. Team 1 pulls with a force of 220 N, while Team 2 pulls with a force of 190 N. The friction force exerted on the box is A. 30 N in the same direction as Team 1's pull. B. 30 N in the same direction as Team 2's pull. C. There are two friction forces, 220 N opposing Team 1's pull and 190 N opposing Team 2's pull. D. The friction force is zero,the box does not move because of its inertia.

B

14. There are three forces acting on an object: 6 N to the left, 5 N to the right, and 3 N to the left. What is the net force acting on the object? A. 4 N B. 4 N left C. 4 N right D. 6 N left

B

17. What are the size and direction of the force that is the sum of a force of 3 N acting south and a force of 6 N acting north? A. 2 N north B. 3 N north C. 6 N north D. 9 N north

B

18. What is the net force acting on an object which is under the influence of a 5 N force acting north and a 5 N force acting west? A. 5 N northwest B. 7 N northwest C. 10 N northwest D. zero

B

23. Forces of 4 N and 6 N act on an object. What is the minimum value for the sum of these two forces? A. zero B. 2 N C. 4 N D. 10 N

B

24. You are analyzing a problem in which two forces act on an object. A 200-N force pulls to the right and a 40-N force pulls to the left. The net force acting on the object is A. 40 N to the left. B. 160 N to the right. C. 200 N to the right. D. 240 N to the right.

B

28. If the net force on a hot-air balloon is directed straight upward, which way does the acceleration point? A. downward B. upward C. upward only if the balloon is rising D. upward and downwind

B

29. If a hot air balloon is descending with decreasing speed, the net force exerted on it must be: A. downward B. upward C. zero

B

30. What kind of motion does a constant, non-zero net force produce on an object of constant mass? A. constant speed B. constant acceleration C. increasing acceleration D. decreasing acceleration

B

36. When the same net force is applied to two blocks, the yellow one has a larger acceleration than the blue one. Which of the following is correct? A. The yellow block has a larger mass. B. The blue block has a larger mass. C. They have the same mass.

B

37. The same net force is applied to two blocks. If the yellow one has a larger mass than the blue one, which one will have the larger acceleration? A. the yellow block B. the blue block C. They have the same acceleration.

B

38. When a net force of 2newtons is applied to a block, a student measures the acceleration of the block to have magnitude ao. If 5 newtons of net force were applied to the same block, the magnitude of its acceleration would be A. ao B. greater than ao but less than 2ao C. 2ao D. greater than 2ao but less than 5ao

B

44. When the same net force is applied to object A and object B, object A has an acceleration three times that of object B. Which of the following is correct? A. Object A has three times the mass of object B. B. Object A has one-third the mass of object B. C. Object A has a different, less streamlined shape than object B. D. Object A has more friction than object B.

B

46. The strength of gravity on the Moon is only 1/6th that on Earth. If an astronaut has a mass of 90 kg on earth, what would her mass be on the Moon? A. 540 kg B. 90 kg C. 15 kg D. 6 kg

B

48. The strength of gravity on the Moon is only 1/6th that on Earth. If an astronaut has a mass of 90 kg on Earth, what would her weight be on the Moon? A. 900 N B. 150 N C. 90 N D. 15 N

B

52. A ball with a weight of 20 N is thrown vertically upward. What is the acceleration of the ball just as it reaches the top of its path? A. zero B. 10 m/s2 downward C. 10 m/s2 upward D. The acceleration cannot be determined.

B

53. A ball falling from a great height will reach terminal speed when its ____ goes to zero. A. inertia B. net force C. weight D. speed

B

54. When a snowflake falls, it quickly reaches a terminal velocity. This happens because A. the mass of the snowflake is too small for gravity to have any effect. B. there is no net force acting on the snowflake. C. the snowflake has no weight. D. the mass of the snowflake is smaller than its weight.

B

55. A parachutist reaches terminal speed when A. her weight goes to zero. B. the force of air resistance equals her weight. C. the force of air resistance exceeds her weight. D. the force of air resistance equals her mass.

B

57. A professor decides to simulate the effects of air resistance by simultaneously dropping two balls in a long column of water. The two balls have the same size but have masses of 1 kg and 2 kg. What happens? A. The 1-kg ball hits the bottom first. B. The 2-kg ball hits the bottom first. C. They hit the bottom at the same time.

B

67. You leap from a bridge with a bungee cord tied around your ankles. As you approach the river below, the bungee cord begins to stretch and you begin to slow down. The force of the cord on your ankles to slow you is ____ the force of your ankles on the cord to stretch it. A. less than B. equal to C. greater than

B

69. Because the forces demanded by Newton's third law of motion are equal in magnitude and opposite in direction, how can anything ever be accelerated? A. Newton's third law only applies when there is NO acceleration. B. The forces in question act on different bodies. C. Newton's second law is more important. D. Third law forces cannot cause accelerations.

B

70. The two forces that make up a Newton's third law force pair A. always appear on the same free-body diagram B. always appear on two different free-body diagrams C. in some cases appear on the same free-body diagram, and in other cases appear on two different free-body diagrams

B

74. Two skaters face each other on perfectly smooth ice. One skater has twice the mass as the other. Assuming that the bigger skater pushes the smaller, which of the following statements is true? A. The bigger skater won't move. B. The bigger skater will move with the smaller acceleration. C. The bigger skater will move with the larger acceleration. D. Both skaters move with the same acceleration.

B

75. Terry and Chris pull hand-over-hand on opposite ends of a rope while standing on a frictionless frozen pond. Terry's mass is 75 kg and Chris's mass is 50 kg. If Terry's acceleration is 2 m/s2, what is Chris's acceleration? A. 2 m/s2 B. 3 m/s2 C. 6 m/s2 D. 10 m/s2

B

77. A child stands on a bathroom scale while riding in an elevator. The child's weight when the elevator is not moving is 500 N. What does the scale read when the elevator free-falls from the tenth floor? A. greater than 500 N B. less than 500 N C. equal to 500 N

B

79. A child stands on a bathroom scale while riding in an elevator. The child's weight when the elevator is not moving is 500 N. What does the scale read as the elevator comes to a stop at the tenth floor on its upward trip? A. greater than 500 N B. less than 500 N C. equal to 500 N

B

81. You are riding an elevator from your tenth-floor apartment to the parking garage in the basement. As you approach the garage, the elevator begins to slow. The net force acting on you is A. always equal to your weight B. directed upward C. directed downward D. zero

B

9. If the force of friction on a child's wagon is 25 N, how much force must be applied to maintain a constant, non-zero velocity? A. 26 N B. 25 N C. 24 N D. zero

B

11. A small block sits on a horizontal table. In one experiment, a student pushes with a horizontal force of 5 N, but the block does not move. In a second experiment, the student glues sandpaper to the base of the block, and once again pushes with a horizontal force of 5 N. The block does not move. The magnitude of the friction force exerted on the block is A. greater in the first experiment B. greater in the second experiment C. the same in the two experiments

C

12. A rectangular block sits on a horizontal table. In one experiment, a student pushes with a horizontal force of 5 N, but the block does not move. In a second experiment, the student tilts the block up so that it is resting on its narrow end, and once again pushes with a horizontal force of 5 N. The block still does not move. The magnitude of the friction force exerted on the block is A. greater in the first experiment B. greater in the second experiment C. the same in the two experiments

C

19. What is the magnitude of the net force acting on an object which is under the influence of a 3 N force acting south and a 4 N force acting east? A. 3 N B. 4 N C. 5 N D. 7 N

C

25. Two skydivers of identical weight are in freefall at terminal speed. The first skydiver has a baggy suit and descends at a speed of 150 mph. The second skydiver has a skintight suit and descends at a speed of 200 mph. The magnitude of the force of air resistance on the second skydiver is A. greater than that on the first skydiver. B. less than that on the first skydiver. C. equal to that on the first skydiver. D. there is not enough information to deteremine this

C

26. A skydiver in freefall at a terminal speed of 180 mph experiences an upward force of 1000 N due to air resistance. The skydiver then opens her parachute, reducing to a new, lower constant speed. The force of air resistance on the skydiver-parachute system is now A. greater than 1000 N B. less than 1000 N C. equal to 1000 N

C

31. If a body is acted on by a force of 10 N and doesn't accelerate, we have to assume A. nothing. That's what should happen. B. its inertia is too large. C. that the net force acting on the body is zero. D. that the law of inertia only holds for large forces.

C

32. If a body is acted on by a force of 10 N and moves in a straight line with constant speed, we have to assume A. nothing. That's what should happen. B. that its inertia is too large for it to speed up. C. that the net force acting on the body is zero. D. that the surface the object sits on must have very low friction.

C

33. If you push on a railroad boxcar with a force of 300 N and it doesn't move, you can conclude that A. Newton's second law is not valid. B. this force is canceled by the third law force. C. the boxcar has too much mass to accelerate. D. there is a total force of 300 N in the opposite direction.

C

45. If the mass and weight of an astronaut are measured on Earth and on the Moon, we will find that the masses are ____ and the weights are ____. A. the same ... the same B. different ... different C. the same ... different D. different ... the same

C

49. The strength of gravity on Mars is only 40% of that on Earth. If a child has a mass of 40 kg on Earth, what would the child's weight be on Mars? A. 16 N B. 40 N C. 160 N D. 400 N

C

5. If an object moves with a constant velocity, we can conclude that A. it is moving toward its natural place. B. there are no forces acting on it. C. there is no unbalanced (net) force acting on it. D. it has a very large inertia.

C

58. A 40-kg crate is being pushed across a horizontal floor. If the coefficient of sliding friction is 0.3, what is the frictional force acting on the crate? A. 12 N B. 40 N C. 120 N D. 400 N

C

59. A crate has a mass of 24 kg. What applied force is required to produce an acceleration of 3 m/s2 if the frictional force is known to be 90 N? A. 72 N B. 90 N C. 162 N D. 240 N

C

61. You apply a 75-N force to pull a child's wagon across the floor at a constant speed of 0.5 m/s. If you increase your pull to 80 N, the wagon will A. continue to move at 0.5 m/s. B. speed up briefly and then move at a faster constant speed. C. move with a continuously increasing speed.

C

62. If F1 is the force exerted on a cart by a horse and F2 is the force exerted on the horse by the cart, then F1 is ____ F2. A. much greater than B. slightly greater than C. equal to D. slightly less than

C

64. A ball with a weight of 40 N is falling freely toward the surface of the Moon. What force does this ball exert on the Moon? A. zero B. 40 N down C. 40 N up

C

65. Which of the following is the third-law force that accompanies the force that an apple exerts on a tree? It is the force that A. Earth exerts on the apple. B. the apple exerts on Earth. C. the tree exerts on the apple. D. the air exerts on the apple.

C

66. A book sits at rest on a table. Which force does Newton's third law tell us is equal and opposite to the gravitational force acting on the book? A. the normal force by the table on the book B. the normal force by the book on the table C. the gravitational force by the book on Earth D. the net force on the book

C

68. You leap from a bridge with a bungee cord tied around your ankles. As you approach the river below, the bungee cord begins to stretch and you begin to slow down. The force of the cord on your ankles to slow you is ____ your weight. A. less than B. equal to C. greater than

C

78. A child stands on a bathroom scale while riding in an elevator. The child's weight when the elevator is not moving is 500 N. What does the scale read when the elevator is moving at a constant speed? A. greater than 500 N B. less than 500 N C. equal to 500 N

C

8. A block is given a quick tap and allowed to slide across a horizontal frictional surface. The subsequent motion will be one with A. decreasing speed. B. increasing speed. C. a constant speed. D. a constant, non-zero acceleration.

C

82. You are riding an elevator from the parking garage in the basement to the tenth floor of an apartment building. As you approach your floor, the elevator begins to slow. The net force acting on you is A. always equal to your weight B. directed upward C. directed downward D. zero

C

otherwise greater

C

the elevator could be moving upward or downward

C

34. You push on a large crate with a horizontal force of 25 N and it moves with constant speed across a concrete floor. If you were to push the same crate on the same floor with a force of 50 N, the crate would A. move with a constant speed twice as great as before. B. move with the same constant speed as before. C. move with increasing speed. D. the mass of the crate must be known in order to answer.

D

4. If an object moves in a straight line with a constant speed, we can conclude that A. the object has inertia. B. there are no forces acting on the object. C. there must be at least two forces acting on the object. D. there is no unbalanced force acting on the object.

D

41. What net force is needed to accelerate a 60-kg ice skater at 2 m/s2? A. zero B. 30 N C. 60 N D. 120 N

D

42. What is the mass of a cart that has an acceleration of 4 m/s2 when a net force of 2000 N is applied to it? A. 8,000 kg B. 2000 kg C. 5000 kg D. 500 kg

D

43. What acceleration is produced by a force of 100 N acting on a mass of 10 kg if its velocity is 20 m/s and the frictional force is 30 N? A. 10 m/s2 B. 9 m/s2 C. 8 m/s2 D. 7 m/s2

D

47. Which of the following is not a vector quantity? A. force B. acceleration C. weight D. mass

D

51. A ball with a weight of 20 N is thrown vertically upward. What are the size and direction of the force on the ball just as it reaches the top of its path? A. zero B. 10 N upward C. 10 N downward D. 20 N downward

D

63. If Earth exerts a gravitational force of 20,000 N on a satellite in synchronous orbit, what force does the satellite exert on Earth? A. zero B. a small fraction of 1 N C. 5000 N D. 20,000 N

D

83. If you stand on a spring scale in your bathroom at home, it reads 600 N, which means your mass is 60 kg. If instead you stand on the scale while accelerating at 2 m/s2 upward in an elevator, what would the scale read? A. 120 N B. 480 N C. 600 N D. 720 N

D

Newton's third law applies to any pair of objects that exert forces on one another

D