Ch 4 Test Q's (07-08)

Chapter 4 (Newtons 3 Laws)

1. A 7 kg bowling ball experiences a net force of 5 N. What will be its acceleration?

a. 35 m/s²

b. 7.0 m/s²

c. 5.0 m/s²

d. 0.71 m/s²

2. An astronaut applies a force of 500 N to an asteroid and it accelerates at 7 m/s². What is the asteroid’s mass?

a. 71 kg

b. 135 kg

c. 441 kg

d. 3500 kg

3. Which of the following is an example of the type of force which acts at a distance?

a. gravitational

b. magnetic

c. electrical

d. all of the above

4. Which of the following expresses a principle which was initially stated by Galileo and was later incorporated into Newton’s laws of motion?

a. An object’s acceleration is inversely proportional to its mass.

b. For every action there is an equal but opposite reaction.

c. The natural condition for a moving object is to remain in motion.

d. The natural condition for a moving object is to come to rest.

5. Two ropes are attached to a 40 kg object. The first rope applies a force of 25 N and the second, 40 N directed. If the two ropes are perpendicular to each other, what is the resultant acceleration of the object?

a. 1.2 m/s²

b. 3.0 m/s²

c. 25 m/s²

d. 47 m/s²

6. Acceleration due to gravity on the moon’s surface is 1/6th that on Earth. An astronaut’s life support backpack weighs 300 lb on Earth. What does it weigh on the moon?

a. 1800 lb

b. 300 lb

c. 135 lb

d. 50 lb

7. A block of mass 5.0 kg rests on a horizontal surface where the coefficient of sliding kinetic friction between the two is 0.2. A string attached to the block is pulled horizontally, resulting in a 2 m/s² acceleration by the block. Find the tension in the string. (g = 9.8 m/s²)

a. 0.2 N

b. 9.8 N

c. 19.8 N

d. 10 N

8. Two blocks joined by a string have masses of 6 and 9 kg. They rest on a frictionless horizontal surface. A 2nd string, attached only to the 9 kg block, has horizontal force = 30 N applied to it. Both blocks accelerate. Find the tension in the string between the blocks.

a. 18 N

b. 28 N

c. 12 N

d. 15 N

9. If we know that a net force is acting on an object, which of the following must we assume regarding the object’s condition? The object is:

a. at rest.

b. moving with a constant velocity.

c. being accelerated.

d. losing mass.

10. If we know an object is moving at constant velocity, we must we assume:

a. There is no net force acting on the object.

b. There are no forces acting on the object.

c. The object is accelerating.

d. The object is losing mass.

11. The statement by Newton that “for every action there is an opposite but equal reaction” is regarded as which of his laws of motion?

a. first

b. second

c. third

d. fourth

12. What condition must apply to a system’s state of motion for it to be regarded as an inertial frame of reference?

a. in decreasing velocity

b. in constant velocity

c. in constant acceleration

d. in increasing acceleration

13. A 2000 kg sail boat experiences an eastward force of 3000 N by the ocean tide and a wind force against its sails with magnitude of 6000 N directed toward the northwest (45˚ N of W). What is the magnitude of the resultant acceleration?

a. 2.2 m/s²

b. 2.1 m/s²

c. 1.5 m/s²

d. 3.0 m/s²

14. A 2000 kg sail boat experiences an eastward force of 3000 N by the ocean tide and a wind force against its sails with magnitude of 6000 N directed toward the northwest (45˚ N of W). What is the direction of the resultant acceleration?

a. 60˚ N of E

b. 30˚ N of W

c. 30˚ N of E

d. 74˚ N of W

15. A cart of weight 20 N is accelerated across a level surface at 0.15 m/s². What net force acts on the wagon? (g = 9.8 m/s²)

a. 0.92 N

b. 0.31 N

c. 3.0 N

d. 4.5 N

16. An airplane of mass 1.2 ´ 10⁴kg tows a glider of mass 0.6 ´ 10⁴ kg. The airplane propellers provide a net forward thrust of 3.6 ´ 10⁴N. What is the glider’s acceleration?

a. 2.0 m/s²

b. 3.0 m/s²

c. 6.0 m/s²

d. 9.8 m/s²

17. Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8 kg mass is another light string which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.5 m/s², then what is the tension in the connecting string between the blocks?

a. 14 N

b. 6 N

c. 10 N

d. 4.0 N

18. Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8 kg mass is another light string which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.5 m/s², what is the tension in the string attached to the 8 kg mass?

a. 14 N

b. 6 N

c. 10 N

d. 4.0 N

19. A 10 kg block and a 2.0 kg hanging mass are connected by a light string over a massless, frictionless pulley. If g = 9.8 m/s², what is the acceleration of the system when released?

a. 2.5 m/s²

b. 6.5 m/s²

c. 7.8 m/s²

d. 9.8 m/s²

20. A 15 kg block rests on a level frictionless surface and is attached by a light string to a 5.0 kg hanging mass where the string passes over a massless frictionless pulley. If g = 9.8 m/s², what is the tension in the connecting string?

a. 65 N

b. 17 N

c. 49 N

d. 36.8 N

21. A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250 kg crate. If g = 9.8 m/s², what is the coefficient of static friction?

a. 3.0

b. 0.15

c. 0.28

d. 0.31

22. A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250 kg crate. What is the acceleration of the crate if the 800 N force is maintained after the crate begins to move and the coefficient of kinetic friction is 0.12?

a. 1.8 m/s²

b. 2.5 m/s²

c. 3.0 m/s²

d. 3.8 m/s²

23. A 100 kg box is placed on a ramp. As one end of the ramp is raised, the box begins to move downward just as the angle of inclination reaches 15˚. What is the coefficient of static friction between box and ramp?

a. 0.15

b. 0.26

c. 0.77

d. 0.95

24. A 300 kg crate is placed on an adjustable inclined plane. As one end of the incline is raised, the crate begins to move downward. If the crate slides down the plane with an acceleration of 0.7 m/s² when the incline angle is 250˚, what is the coefficient of kinetic friction between ramp and crate? (g = 9.8 m/s²)

a. 0.47

b. 0.42

c. 0.39

d. 0.12

25. A 250 kg crate is placed on an adjustable inclined plane. If the crate slides down the incline with an acceleration of 0.7 m/s² when the incline angle is 25˚, then what should the incline angle for the crate to slide down the plane at constant speed? (g = 9.8 m/s²)

a. 12˚

b. 21˚

c. 25˚

d. 29˚

26. A rock is rolled in the sand. It starts at 5 m/s, moves in a straight line for a distance of 3 m, and then stops. What is the average acceleration?

a. 1.8 m/s²

b. 4.2 m/s²

c. 5.4 m/s²

d. 6.2 m/s²

27. Doug hits a hockey puck, giving it an initial velocity of 6.0 m/s. If the coefficient of kinetic friction between ice and puck is 0.05, how far will the puck slide before stopping?

a. 19 m

b. 25 m

c. 37 m

d. 57 m

28. Rita accelerates a 0.4 kg ball from rest to 9 m/s during the 0.15 s in which her foot is in contact with the ball. What average force does she apply to the ball during the kick?

a. 48 N

b. 72 N

c. 24 N

d. 60 N

29. An elevator weighing 20,000 N is supported by a steel cable. What is the tension in the cable when the elevator is being accelerated upward at a rate of 3.0 m/s²? (g = 9.8 m/s²)

a. 13,900 N

b. 23,100 N

c. 20,000 N

d. 26,100 N

30. It is late and Carlos is sliding down a rope from his third floor window to meet his friend Juan. As he slides down the rope faster and faster, he becomes frightened and grabs harder on the rope, increasing the tension in the rope. As soon as the upward tension in the rope becomes equal to his weight:

a. Carlos will stop.

b. Carlos will slow down.

c. Carlos will continue down at a constant velocity.

d. the rope must break.

31. A thrown stone hits a window, but doesn’t break it. Instead it reverses direction and ends up on the ground below the window. Since the stone did not break the glass, we know:

a. the force of the brick on the glass > the force of the glass on the brick.

b. the force of the brick on the glass = the force of the glass on the brick.

c. the force of the brick on the glass < the force of the glass on the brick.

d. the brick didn’t slow down as it broke the glass.

32. As a basketball player starts to jump for a rebound, he begins to move upward faster and faster until he leaves the floor. During this time that he is in contact with the floor, the force of the floor on his shoes is:

a. bigger than his weight.

b. equal in magnitude and opposite in direction to his weight.

c. less than his weight.

d. zero.

33. As I slide a box at constant speed up a frictionless slope, pulling parallel to the slope, the tension in the rope will be:

a. greater than the tension would be if the box were stationary.

b. greater than the weight of the box.

c. equal to the weight of the box.

d. less than the weight of the box.

34. A boxcar of mass 200 tons at rest becomes uncoupled on a 10˚ grade. If the track is considered to be frictionless, what velocity does the boxcar have after 10 seconds?

a. 0.37 m/s

b. 0.59 m/s

c. 1.3 m/s

d. 4.3 m/s

35. As a car goes up a hill, there is a force of friction between the road and the tires rolling on the road. The maximum force of friction is equal to:

a. the weight of the car times the coefficient of kinetic friction.

b. the normal force of the road times the coefficient of kinetic friction.

c. the normal force of the road times the coefficient of static friction.

d. zero.

36. As a car moves forward on a level road at constant velocity, the total force acting on the tires is:

a. greater than the normal force times the coefficient of static friction.

b. equal to the normal force times the coefficient of static friction.

c. the normal force times the coefficient of kinetic friction.

d. zero.

37. As a car skids with its wheels locked trying to stop on a road covered with ice and snow, the force of friction between the icy road and the tires will usually be:

a. greater than the normal force of the road times the coefficient of static friction.

b. equal to the normal force of the road times the coefficient of static friction.

c. less than the normal force of the road times the coefficient of static friction.

d. greater than the normal force of the road times the coefficient of kinetic friction.

38. There are six books in a stack, each with a weight of 5 N. The coefficient of friction between all the books is 0.2. With what horizontal force must I push to start sliding the top five books off the bottom one?

a. 1.0 N

b. 5.0 N

c. 3.0 N

d. 7.0 N

39. There are six books in a stack, each with weight 5 N. The coefficient of friction between all the books is 0.2. With what horizontal force must I push to start sliding the fifth book out of the stack, leaving the top four and the sixth book behind?

a. 1.0 N

b. 5.0 N

c. 3.0 N

d. 7.0 N

40. As a 3.0 kg bucket is being lowered into a 10 m deep well, starting from the top, the tension in the rope is 9.8 N. The acceleration of the bucket will be:

a. 6.5 m/s² downward

b. 9.8 m/s² downward

c. zero

d. 3.3 m/s²upward

41. A 70‑kg man jumps 1 m down onto a concrete walkway. His downward motion stops in 0.02 seconds. If he forgets to bend his knees, what force is transmitted to his leg bones?

a. 15,490 N

b. 7,010 N

c. 4,900 N

d. 3,500 N

42. A man pulls a sled at a constant velocity across a horizontal snow surface. If a force of 80 N is being applied to the sled rope at an angle of 53˚ to the ground, what is the force of friction between sled and snow?

a. 80 N

b. 64 N

c. 48 N

d. 40 N

43. A trapeze artist, with swing, weighs 800 N; he is momentarily held to one side by his partner so that the swing ropes make an angle of 30˚ with the vertical. In such a condition of static equilibrium, what is the horizontal force being applied by the partner?

a. 924 N

b. 400 N

c. 196 N

d. 461 N

44. A trapeze artist, with swing, weighs 800 N; he is being held to one side by his partner so that the swing ropes make an angle of 30˚ with the vertical. In such a condition of static equilibrium what is the tension in the rope?

a. 924 N

b. 400 N

c. 196 N

d. 461 N

45. A 15 N crate rests on an ramp; the maximum angle just before it slips is 25˚ with the horizontal. What is the coefficient of static friction between crate and ramp surfaces?

a. 0.11

b. 0.21

c. 0.38

d. 0.47

46. A 5000 N weight is held suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T₁. Cable 2 applies a force upward and to the left at an angle of 37˚ to the negative ´‑axis and has a tension, T₂. What is the tension, T₁?

a. 4000 N

b. 6640 N

c. 8310 N

d. 3340 N

47. A 5000 N weight is suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T₁. Cable 2 applies a force upward and to the left at an angle of 37˚ to the negative ´‑axis and has a tension, T₂. Find T_2.

a. 4000 N

b. 6640 N

c. 8310 N

d. 3340 N

48. A sled weighs 100 N. It is held in place on a frictionless 20 degree slope by a rope attached to a stake at the top; the rope is parallel to the slope. Find the tension in the rope.

a. 94 N

b. 47 N

c. 37 N

d. 34 N

49. A sled weighs 100 N. It is held in place on a frictionless 20 degree slope by a rope attached to a stake at the top; the rope is parallel to the slope. What is the normal force of the slope acting on the sled?

a. 94 N

b. 47 N

c. 37 N

d. 34 N

50. A 150 N sled is pulled up a 28° slope at a constant speed by a force of 100 N. What is the coefficient of kinetic friction between sled and slope?

a. 0.53

b. 0.22

c. 0.13

d. 0.33

51. Jamal pulls a 150 N sled up a 28° slope at constant speed by a force of 100 N. Near the top of the hill he releases the sled. With what acceleration does the sled go down the hill?

a. 1.20 m/s

b. 1.67 m/s

c. 2.22 m/s

d. 2.67 m/s

52. A 500 N tightrope walker stands at the center of the rope such that each half of the rope makes an angle of 10˚ with the horizontal. What is the tension in the rope?

a. 1440 N

b. 1000 N

c. 500 N

d. 2900 N

53. A 500 N tightrope walker stands at the center of the rope. If the rope can withstand a tension of 1800 N without breaking, what is the minimum angle the rope can make with the horizontal?

a. 4˚

b. 8˚

c. 10˚

d. 15˚

54. A 20‑kg traffic light hangs midway on a cable between two poles 40 meters apart. If the sag in the cable is 0.4 meters, what is the tension in each side of the cable?

a. 12,000 N

b. 9,800 N

c. 4,900 N

d. 980 N

55. A girl is using a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30˚ above the horizontal and the tension in the rope is 100 N. What is the normal force of the floor on the box?

a. 300 N

b. 86 N

c. 50 N

d. 250 N

56. Dana uses a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30˚ above the horizontal and the tension in the rope is 100 N. What is the coefficient of friction?

a. 0.34

b. 0.29

c. 0.17

d. 0.20

57. Hector drives a pickup truck horizontally at 15 m/s. He is transporting a crate of delicate lead crystal. If the coefficient of static friction between the crate and the truckbed is 0.40, what is the minimum stopping distance for the truck so the crate will not slide?

a. 28.7 m

b. 51.0 m

c. 33.6 m

d. 44.4 m

58. The coefficient of friction between a racecar’s wheels and the track is 1. The car starts from rest and accelerates at a constant rate for 400 m. Find velocity at the end of the race.

a. 44 m/s

b. 66 m/s

c. 88 m/s

d. 99 m/s

59. A karate‑master strikes a board with an initial velocity of 10 m/s, decreasing to 1 m/s as his hand passes through the board. If the time‑of‑contact with the board is 0.002 s, and the mass of the coordinated hand and arm is 1 kg, what is the force exerted on the board?

a. 1000 N

b. 1800 N

c. 2700 N

d. 4500 N

60. The accelerating force of the wind on a small 200 kg sailboat is 707 N northeast. If the drag of the keel is 500 N acting west, what is the acceleration of the boat?

a. 1.5 m/s² due East

b. 2.5 m/s² due North

c. 3.0 m/s² Northeast

d. 2.0 m/s² North by Northwest

61. A barefoot field‑goal kicker imparts a velocity of 30 m/s to a football at rest. If the football has a mass of 0.5 kg and time‑of‑contact with the football is 0.025 s, what is the force exerted on the foot?

a. 188 N

b. 375 N

c. 600 N

d. 900 N

62. A worker pulls a 200 N packing crate at constant velocity across a rough floor by exerting a force F = 55 N at an angle of 35˚ above the horizontal. What is the coefficient of kinetic friction of the floor?

a. 0.133

b. 0.267

c. 0.400

d. 0.200

63. An automobile of mass 2000 kg moving at 30 m/s, is braked suddenly, with a constant braking force of 10,000 N. How far does the car travel before stopping?

a. 45 m

b. 90 m

c. 135 m

d. 180 m

64. A shotputter moves his arm and the 7 kg shot through a distance of 1 m, giving the shot a velocity of 10 m/s from rest. Find the average force exerted on the shot during this time.

a. 175 N

b. 350 N

c. 525 N

d. 700 N

65. A baseball batter hits an incoming 40 m/s fastball. The ball leaves the bat at 50 m/s after a ball‑on‑bat contact time of 0.03 s. What is the force exerted on the 0.15 kg baseball?

a. 450 N

b. 250 N

c. 200 N

d. 90 N

66. A hockey puck moving at 7 m/s coasts to a halt in 75 m on a smooth ice surface. What is the coefficient of friction between the ice and the puck?

a. µ = 0.025

b. µ = 0.033

c. µ = 0.12

d. µ = 0.25

67. An Olympic skier moving at 20 m/s down a 30˚ slope encounters a region of wet snow, of coefficient of friction µ_k = 0.74. How far down the slope does she go before stopping?

a. 119 m

b. 145 m

c. 170 m

d. 199 m

68. Find the tension in an elevator cable if the 1000 kg elevator is descending with an acceleration of 1.8 m/s², downward.

a. 5,700 N

b. 8,000 N

c. 9,800 N

d. 11,600 N

69. The coefficient of static friction between the tires of a car and the street is µ_s = 0.77. What is the steepest angle of a street q, on which a car can be parked (with wheels locked) without slipping?

a. 22.5˚

b. 30˚

c. 37˚

d. 45˚

70. A 9 kg hanging weight is connected by a string over a pulley to a 5 kg block sliding on a flat table. If the coefficient of sliding friction is 0.2, find the tension in the string.