LAHS Physics Semester 1 Final Practice Multiple Choice

Transcription

1 LAHS Physics Semester 1 Final Practice Multiple Choice The following Multiple Choice problems are practice MC for the final. Some or none of these problems may appear on the real exam. Answers are provided on the last pages. Use the following to answer questions 1-2: An object is moving along a straight line. The graph shows the object's position from the starting point as a function of time. 1. In which segments(s) of the graph does the object have the highest speed? A) AB B) BC C) CD D) DE E) AB and CD 2. At which time(s) does the object reverse its direction of motion? A) 1 s and 2 s B) 2 s and 5 s C) 1 s D) 2 s E) 5 s Use the following to answer question 3: A rock, dropped from rest near the surface of an atmosphere-free planet, attains a speed of 20.0 m/s after falling 8.0 meters. 3. What is the magnitude of the acceleration due to gravity on the surface of this planet? A) 0.40 m/s 2 B) 1.3 m/s 2 C) 2.5 m/s 2 D) 25 m/s 2 E) 160 m/s 2 Page 1

2 4. The minimum takeoff speed for a certain airplane is 75 m/s. What minimum acceleration is required if the plane must leave a runway of length 950 m? Assume the plane starts from rest at one end of the runway. A) 1.5 m/s 2 B) 3.0 m/s 2 C) 4.5 m/s 2 D) 6.0 m/s 2 E) 7.5 m/s 2 5. A car traveling along a road begins accelerating with a constant acceleration of 1.5 m/s 2 in the direction of motion. After traveling 392 m at this acceleration, its speed is 35 m/s. Determine the speed of the car when it began accelerating. A) 1.5 m/s B) 7.0 m/s C) 34 m/s D) 49 m/s E) 2.3 m/s 6. The rate at which the acceleration of an object changes with time is called the jerk. What is the dimension of the jerk? 2 A) [L] [L] 2 [T] [T] D) B) C) [L] [T] 2 E) [L] [T] 3 [L] [ T] 2 3 Use the following to answer question 7: An object is moving along the x axis. The graph shows its position from the starting point as a function of time. Various segments of the graph are identified by the letters A, B, C, and D. Page 2

3 7. What is the velocity of the object at t = 7.0 s? A) +3.0 m/s B) 1.0 m/s C) 2.0 m/s D) 3.0 m/s E) zero Use the following to answer questions 8-9: An object is moving along a straight line in the positive x direction. The graph shows its position from the starting point as a function of time. Various segments of the graph are identified by the letters A, B, C, and D. 8. What was the instantaneous velocity of the object at the end of the eighth second? A) +7.5 m/s B) m/s C) 0.94 m/s D) +1.1 m/s E) 0 m/s 9. Which segment(s) of the graph represent(s) a constant velocity of +1.0 m/s? A) A B) B C) C D) D E) A and C 10. A truck accelerates from rest at point A with constant acceleration of magnitude a and subsequently passes points B and C as shown in the figure. The distance between points B and C is x, and the time required for the truck to travel from B to C is t. Which expression determines the average speed of the truck between the points B and C? A) v 2 = 2ax B) Page 3

4 v = x t C) v = xt D) v = 1 2 at 2 E) v = at 11.A train passes through a town with a constant speed of 16 m/s. After leaving the town, the train accelerates at 0.33 m/s 2 until it reaches a speed of 35 m/s. How far did the train travel while it was accelerating? A) km B) 0.53 km C) 1.5 km D) 2.3 km E) 3.0 km Use the following to answer question 12: A tennis ball is shot vertically upward from the surface of an atmosphere-free planet with an initial speed of 20.0 m/s. One second later, the ball has an instantaneous velocity in the upward direction of 15.0 m/s. 12. Determine the velocity of the ball when it returns to its original position. Note: assume the upward direction is positive. A) +20 m/s B) 20 m/s C) +40 m/s D) 40 m/s E) zero Use the following to answer question 13: The figure shows the speed as a function of time for an object in free fall near the surface of the earth. The object was dropped from rest in a long evacuated cylinder. Page 4

5 13. Which one of the following statements best explains why the graph goes through the origin? A) The object was in a vacuum. B) The object was dropped from rest. C) The velocity of the object was constant. D) All v vs. t curves pass through the origin. E) The acceleration of the object was constant. 14. A car is stopped at a red traffic light. When the light turns to green, the car has a constant acceleration and crosses the 9.10-m intersection in 2.47 s. What is the magnitude of the car's acceleration? A) 1.77 m/s 2 B) 2.98 m/s 2 C) 3.60 m/s 2 D) 7.36 m/s 2 E) 9.80 m/s A landing airplane makes contact with the runway with a speed of 78.0 m/s and moves toward the south. After 18.5 seconds, the airplane comes to rest. What is the average acceleration of the airplane during the landing? A) 2.11 m/s 2, north D) 4.22 m/s 2, south B) 2.11 m/s 2, south E) 14.3 m/s 2, north C) 4.22 m/s 2, north Use the following to answer question 16: Peter noticed a bug crawling along a meter stick and decided to record the bug's position in five-second intervals. After the bug crawled off the meter stick, Peter created the table shown. Page 5

6 16. What is the total distance that the bug traveled between t = 0.00 s and t = 20.0 s? Assume the bug only changed directions at the end of a five-second interval. A) 39.9 cm B) 65.7 cm C) 16.1 cm D) 47.1 cm E) 26.5 cm Use the following to answer question 17: A 10.0-kg crate slides along a horizontal frictionless surface at a constant speed of 4.0 m/s. The crate then slides down a frictionless incline and across a second horizontal surface as shown in the figure. 17. What minimum coefficient of kinetic friction is required to bring the crate to a stop over a distance of 5.0 m along the lower surface? A) 0.30 B) 0.32 C) 0.60 D) 0.66 E) 0.76 Use the following to answer question 18: A rope exerts a force F on a 20.0-kg crate. The crate starts from rest and accelerates upward at 5.00 m/s 2 near the surface of the earth. Page 6

7 18. How much work was done by the force F in raising the crate 4.0 m above the floor? A) 399 J B) 250 J C) 116 J D) 704 J E) 1180 J 19. A cheetah is walking at a speed of 1.10 m/s when it observes a gazelle 41.0 m directly ahead. If the cheetah accelerates at 9.55 m/s 2, how long does it take the cheetah to reach the gazelle if the gazelle doesn't move? A) 4.29 s B) 3.67 s C) 3.05 s D) 1.94 s E) 2.82 s 20. A ball is thrown vertically upward from the surface of the earth. Consider the following quantities: (1) the speed of the ball; (2) the velocity of the ball; (3) the acceleration of the ball. Which of these is (are) zero when the ball has reached the maximum height? A) 1 only B) 2 only C) 1 and 2 D) 1 and 3 E) 1, 2, and 3 Use the following to answer question 21: A projectile is fired horizontally with an initial speed of 50.0 m/s. Neglect air resistance. 21. What is the magnitude of the acceleration of the projectile 3.00 s after it is fired? A) 9.8 m/s 2 B) 16.6 m/s 2 C) 29.4 m/s 2 D) 5.42 m/s 2 E) 4.07 m/s Two cars A and B approach each other at an intersection. Car A is traveling south at 20 m/s, while car B is traveling east at 17 m/s. What is the velocity of car A as described by the passengers in car B? A) 37 m/s, eastward D) 26 m/s, 50 south of west B) 26 m/s, 40 south of east E) 26 m/s, 40 south of west C) 26 m/s, 50 south of east 23. A quarterback throws a pass at an angle of 35 above the horizontal with an initial speed of 25 m/s. The ball is caught by the receiver 2.55 seconds later. Determine the distance the ball was thrown. Page 7

8 A) 13 m B) 18 m C) 36 m D) 52 m E) 72 m Use the following to answer question 24: A shell is fired with a horizontal velocity in the positive x direction from the top of an 80 m high cliff. The shell strikes the ground 1330 m from the base of the cliff. 24. What is the speed of the shell as it hits the ground? A) 4.0 m/s B) 9.8 m/s C) 82 m/s D) 170 m/s E) 330 m/s 25. A basketball player is running at a constant speed of 2.5 m/s when he tosses a basketball upward with a speed of 6.0 m/s. How far does the player run before he catches the ball? Ignore air resistance. A) 3.1 m B) 4.5 m C) The ball cannot be caught because it will fall behind the player. D) 6.0 m E) 7.5 m Use the following to answer questions 26-28: A projectile is fired from a gun and has initial horizontal and vertical components of velocity equal to 30 m/s and 40 m/s, respectively. 26. What is the acceleration of the projectile when it reaches its maximum height? A) 0 m/s 2 B) 9.8 m/s 2, downward C) 4.9 m/s 2, downward Page 8

9 D) less than 9.8 m/s 2 and non-zero. E) Its magnitude is 9.8 m/s 2 and; its direction is changing. 27. What is the speed of the projectile when it is at the highest point in its trajectory? A) 0 m/s B) 20 m/s C) 30 m/s D) 40 m/s E) 50 m/s 28. Approximately how long does it take the projectile to reach the highest point in its trajectory? A) 1 s B) 2 s C) 4 s D) 8 s E) 16 s 29. A boat that can travel at 4.0 km/h in still water crosses a river with a current of 2.0 km/h. At what angle must the boat be pointed upstream (that is, relative to its actual path) to go straight across the river? A) 27 B) 30 C) 60 D) 63 E) A cannonball is aimed 30.0 above the horizontal and is fired with an initial speed of 125 m/s at ground level. How far away from the cannon will the cannonball hit the ground? A) 125 m B) 138 m C) 695 m D) 1040 m E) 1380 m Use the following to answer questions 31-33: A tennis ball is thrown upward at an angle from point A. It follows a parabolic trajectory and hits the ground at point D. At the instant shown, the ball is at point B. Point C represents the highest position of the ball above the ground. Page 9

10 31. Which statement is true concerning the ball when it is at C, the highest point in its trajectory? A) The ball's velocity and acceleration are both zero. B) The ball's velocity is perpendicular to its acceleration. C) The ball's velocity is not zero, but its acceleration is zero. D) The ball's velocity is zero, but its acceleration is not zero. E) The horizontal and vertical components of the ball's velocity are equal. 32. At which point is the velocity vector changing most rapidly with time? A) A B) B C) C D) D E) It is changing at the same rate at all four points. 33. How do the x and y components of the velocity vector of the ball compare at the points B and C? A) The velocity components are non-zero at B and zero at C. B) The x components are the same; the y component at C is 0 m/s. C) The x components are the same; the y component has a larger magnitude at C than at B. D) The x component is larger at C than at B; the y component at B points up while at C, it points downward. E) The x component is larger at B than at C; the y component at B points down while at C, it points upward. 34. A bullet is aimed at a target on the wall a distance L away from the firing position. Because of gravity, the bullet strikes the wall a distance y below the mark as suggested in the figure. Note: The drawing is not to scale. If the distance L were half as large, and the bullet had the same initial velocity, how would y be affected? A) It will double. B) It will be half as large. Page 10

11 C) It will be four times larger. D) It will be one fourth as large. E) It is not possible to determine unless numerical values are given for the distances. 35. A train travels due south at 60 m/s. It reverses its direction and travels due north at 60 m/s. What is the change in velocity of the train? A) 120 m/s, due north D) 60 m/s, due south B) 120 m/s, due south E) 0 m/s C) 60 m/s, due north Use the following to answer questions 36-38: A small boat travels 80.0 km north and then travels 60.0 km east in 1.0 hour. 36. What is the boat's average speed during the one-hour trip? A) 20 km/h B) 100 km/h C) 140 km/h D) 280 km/h E) km/h 37. What is the direction of the boat's average velocity for the one-hour trip? A) due east D) 49.2 north of east B) 36.9 north of east E) 53.1 north of east C) 41.7 north of east 38. What is the boat's displacement for the one-hour trip? A) 20 km B) 100 km C) 140 km D) 280 km E) km 39. A ball is fired at an angle of 45, the angle that yields the maximum range in the absence of air resistance. What is the ratio of the ball's maximum height to its range? A) 1.0 B) 0.75 C) 0.67 D) 0.50 E) 0.25 Use the following to answer question 40: A projectile is fired at an angle of 60.0 above the horizontal with an initial speed of 30.0 m/s. 40. What is the magnitude of the horizontal component of the projectile's displacement at the end of 2 s? Page 11

12 A) 30 m B) 40 m C) 10 m D) 20 m E) 50 m Use the following to answer question 41: A force P pulls on a crate of mass m on a rough surface. The figure shows the magnitudes and directions of the forces that act on the crate in this situation. W represents the weight of the crate. F N represents the normal force on the crate, and f represents the frictional force. 41. Which statement best describes the motion of the crate? A) The crate must be at rest. B) The crate must be moving with constant velocity. C) The crate must be moving with constant acceleration. D) The crate may be either at rest or moving with constant velocity. E) The crate may be either at rest or moving with constant acceleration. 42. In an experiment with a block of wood on an inclined plane, with dimensions shown in the figure, the following observations are made: (1) If the block is placed on the inclined plane, it remains there at rest. (2) If the block is given a small push, it will accelerate toward the bottom of the incline without any further pushing. Which is the best conclusion that can be drawn from these observations? A) The coefficient of kinetic friction must be negative. B) Both coefficients of friction must be less than C) Both coefficients of friction must be greater than Page 12

13 D) The coefficient of static friction must be less than the coefficient of kinetic friction. E) The coefficient of static friction is greater than 0.25 while the coefficient of kinetic friction is less than Use the following to answer question 43: A block is pulled along a rough level surface at constant speed by the force P. The figure shows the free-body diagram for the block. F N represents the normal force on the block; and f represents the force of kinetic friction. 43. What is the magnitude of F N? A) mg B) P C) f D) 2mg E) This cannot be determined from the information given. 44. The wheels of an automobile are locked as it slides to a stop from an initial speed of 30.0 m/s. If the coefficient of kinetic friction is and the road is horizontal, approximately how long does it take the car to stop? A) 6.00 s B) 7.57 s C) 15.3 s D) 22.5 s E) 30.0 s 45. The graph shows the velocities of two objects of equal mass as a function of time. Forces F A, F B, and F C acted on the objects during intervals A, B, and C, respectively. Page 13

14 Which one of the following choices is the correct relationship between the magnitudes of the forces? A) F B = F C > F A D) F A = F B = F C B) F C > F B > F A E) F A > F B > F C C) F A > F B = F C Use the following to answer question 46: A 2.0-N force acts horizontally on a 10-N block that is initially at rest on a horizontal surface. The coefficient of static friction between the block and the surface is What is the magnitude of the frictional force that acts on the block? A) 0 N B) 2 N C) 5 N D) 8 N E) 10 N Use the following to answer question 47: A 10-kg block is connected to a 40-kg block as shown in the figure. The surface on which the blocks slide is frictionless. A force of 50 N pulls the blocks to the right. 47. What is the magnitude of the tension T in the rope that connects the two blocks? A) 0 N B) 10 N C) 20 N D) 40 N E) 50 N 48. Two forces act on a hockey puck. For which orientation of the forces will the puck acquire an acceleration with the largest magnitude? Page 14

15 (e) The magnitude of the acceleration will be the same in all four cases shown above. 49. A rock is suspended from a string; and it moves downward at constant speed. Which one of the following statements is true concerning the tension in the string if air resistance is not ignored? A) The tension is zero newtons. B) The tension points downward. C) The tension is equal to the weight of the rock. D) The tension is less than the weight of the rock. E) The tension is greater than the weight of the rock. 50. A crate rests on the flatbed of a truck that is initially traveling at 15 m/s on a level road. The driver applies the brakes and the truck is brought to a halt in a distance of 38 m. If the deceleration of the truck is constant, what is the minimum coefficient of friction between the crate and the truck that is required to keep the crate from sliding? A) 0.20 B) 0.30 C) 0.39 D) 0.59 E) This cannot be determined without knowing the mass of the crate. Use the following to answer question 51: A block of mass M is held motionless on a frictionless inclined plane by means of a string attached to a vertical wall as shown in the drawing. Page 15

16 51. If the string breaks, what is the magnitude of the acceleration of the block as it slides down the inclined plane? A) zero m/s 2 B) g C) g cos θ D) g sin θ E) g tan θ Use the following to answer question 52: A physics student in a hot air balloon ascends vertically at constant speed. Consider the following four forces that arise in this situation: F 1 = the weight of the hot air balloon F 2 = the weight of the student F 3 = the force of the student pulling on the earth F 4 = the force of the hot air balloon pulling on the student 52. Which two forces form an "action-reaction" pair that obeys Newton's third law? A) F 1 and F 2 B) F 2 and F 3 C) F 1 and F 3 D) F 2 and F 4 E) F 3 and F 4 Use the following to answer question 53: A block is at rest on a rough inclined plane and is connected to an object with the same mass as shown. The rope may be considered massless; and the pulley may be considered frictionless. The coefficient of static friction between the block and the plane is µ s ; and the coefficient of kinetic friction is µ k. 53. If the rope were cut between the block and the pulley, what would be the magnitude of the acceleration of the block down the plane? A) g D) g(tan θ µ k sin θ) B) g µ k sin θ E) g(sin θ µ k cos θ) C) g µ k cos θ Page 16

17 54. A net force F is required to give an object with mass m an acceleration a. If a net force 6F is applied to an object with mass 2m, what is the acceleration on this object? A) a B) 2a C) 3a D) 4a E) 6a 55. A rock is suspended from a string; and it accelerates downward. Which one of the following statements concerning the tension in the string is true? A) The tension points downward. B) The tension is less than the weight of the rock. C) The tension is equal to the weight of the rock. D) The tension is greater than the weight of the rock. E) The tension is independent of the magnitude of the rock's acceleration. 56. A block of weight W is suspended by a string of fixed length. The ends of the string are held at various positions as shown in the figures below. In which case, if any, is magnitude of the tension along the string the largest?. (e) It will be the same in all four cases, since the string must support the entire weight of the block. 57. When the net force that acts on a hockey puck is 10 N, the puck accelerates at a rate of 50 m/s 2. Determine the mass of the puck. A) 0.2 kg B) 1.0 kg C) 5 kg D) 10 kg E) 50 kg 58. A 2.0-N rock slides on a frictionless inclined plane. Which one of the following statements is true concerning the normal force that the plane exerts on the rock? Page 17

18 A) The normal force is zero newtons. B) The normal force is 2.0 N. C) The normal force is greater than 2.0 N. D) It increases as the angle of inclination, θ, is increased. E) The normal force is less than 2.0 N, but greater than zero newtons. Use the following to answer question 59: Two 5-N boxes are attached to opposite ends of a spring scale and suspended from pulleys as shown. 59. Suppose that the system were placed in an elevator that accelerated downward at 2 m/s 2. What would the scale read? A) 0 N B) 4 N C) 6 N D) 8 N E) 10 N 60. A 4-kg block is connected by means of a massless rope to a 2-kg block as shown in the figure. Complete the following statement: If the 4-kg block is to begin sliding, the coefficient of static friction between the 4-kg block and the surface must be A) less than zero. D) greater than 0.5, but less than 1. B) greater than 2. E) less than 0.5, but greater than zero. C) greater than 1, but less than 2. Use the following to answer questions 61-62: A 1500-kg car travels at a constant speed of 22 m/s around a circular track that has a radius of Page 18

19 85 m. 61. Which statement is true concerning this car? A) The velocity of the car is changing. B) The car is characterized by constant velocity. C) The car is characterized by constant acceleration. D) The car has a velocity vector that points along the radius of the circle. E) The car has an acceleration vector that is tangent to the circle at all times. 62. What is the magnitude of the acceleration of the car? A) 5.7 m/s 2 B) 0.26 m/s 2 C) 9.8 m/s 2 D) 1.2 m/s 2 E) zero m/s A car traveling at 20 m/s rounds a curve so that its centripetal acceleration is 5 m/s 2. What is the radius of the curve? A) 4 m B) 8 m C) 80 m D) 160 m E) 640 m Use the following to answer question 64: A small car of mass M travels along a straight, horizontal track. As suggested in the figure, the track then bends into a vertical circle of radius R. 64. What is the minimum acceleration that the car must have at the top of the track if it is to remain in contact with the track? A) 4.9 m/s 2, downward D) 9.8 m/s 2, downward B) 4.9 m/s 2, upward E) 19.6 m/s 2, upward C) 9.8 m/s 2, upward 65. A spaceship is in orbit around the earth at an altitude of miles. Which one of the Page 19

20 following statements best explains why the astronauts experience "weightlessness?" A) The centripetal force of the earth on the astronaut in orbit is zero newtons. B) The pull of the earth on the spaceship is canceled by the pull of the other planets. C) The spaceship is in free fall and its floor cannot press upwards on the astronauts. D) The force of gravity decreases as the inverse square of the distance from the earth's center. E) The force of the earth on the spaceship and the force of the spaceship on the earth cancel because they are equal in magnitude but opposite in direction. 66. A boy is whirling a stone around his head by means of a string. The string makes one complete revolution every second, and the tension in the string is F T. The boy then speeds up the stone, keeping the radius of the circle unchanged, so that the string makes two complete revolutions every second. What happens to the tension in the sting? A) The tension is unchanged. B) The tension reduces to half of its original value. C) The tension increases to twice its original value. D) The tension increases to four times its original value. E) The tension reduces to one-fourth of its original value. 67. What is the acceleration due to gravity at an altitude of m above the earth's surface? Note: the radius of the earth is m. A) 3.99 m/s 2 B) 9.80 m/s 2 C) 5.00 m/s 2 D) 6.77 m/s 2 E) 7.32 m/s Which force is responsible for holding a car in a frictionless banked curve? A) the reaction force to the car's weight B) the vertical component of the car's weight C) the vertical component of the normal force D) the horizontal component of the car's weight E) the horizontal component of the normal force 69. The second hand on a watch has a length of 4.50 mm and makes one revolution in s. What is the speed of the end of the second hand as it moves in uniform circular motion? A) m/s D) m/s B) m/s E) m/s C) m/s Page 20

21 70. The radius of the earth is m and its mass is kg. What is the acceleration due to gravity at a height of m above the earth's surface? A) 1.08 m/s 2 B) 2.15 m/s 2 C) 9.80 m/s 2 D) m/s 2 E) m/s A car enters a horizontal, curved roadbed of radius 50 m. The coefficient of static friction between the tires and the roadbed is What is the maximum speed with which the car can safely negotiate the unbanked curve? A) 5 m/s B) 10 m/s C) 20 m/s D) 40 m/s E) 100 m/s 72. The mass and radius of the moon are kg and m, respectively. What is the weight of a 1.0-kg object on the surface of the moon? A) 1.0 N B) 1.7 N C) 3.7 N D) 8.8 N E) 9.8 N 73. Jupiter has a mass that is roughly 320 times that of the Earth and a radius equal to 11 times that of the Earth. What is the acceleration due to gravity on the surface of Jupiter? A) 2.7 m/s 2 B) 9.8 m/s 2 C) 26 m/s 2 D) 87 m/s 2 E) 260 m/s The record for the highest speed achieved in a laboratory for a uniformly rotating object was m/s for a 0.15-m long carbon rod. What was the period of rotation of the rod? A) s B) s C) s D) s E) s 75. The orbital radius about the Sun of Saturn is about 10 times that of Earth. Complete the following statement: The period of Saturn is about A) 6 yr. B) 30 yr. C) 40 yr. D) 90 yr. E) 160 yr. 76. Approximately one billion years ago, the Moon orbited the Earth much closer than it does today. The radius of the orbit was only km. Today, the radius is km. The orbital period was only s. The present period is s. Assume that the orbit of the Moon is circular. Calculate the ratio of the speed of the Moon in its ancient orbit to the speed that it has today. A) 15.8 B) 12.8 C) 10.2 D) 7.15 E) 6.39 Page 21

22 77. Determine the minimum angle at which a roadbed should be banked so that a car traveling at 20.0 m/s can safely negotiate the curve if the radius of the curve is m. A) B) C) 11.5 D) 19.6 E) A ball is whirled on the end of a string in a horizontal circle of radius R at constant speed v. The centripetal acceleration of the ball can be increased by a factor of 4 by A) keeping the speed fixed and increasing the radius by a factor of 4. B) keeping the radius fixed and increasing the speed by a factor of 4. C) keeping the radius fixed and increasing the period by a factor of 4. D) keeping the radius fixed and decreasing the period by a factor of 4. E) keeping the speed fixed and decreasing the radius by a factor of Consider a satellite in a circular orbit around the Earth. If it were at an altitude equal to twice the radius of the Earth, 2R E, how would its speed v be related to the Earth's radius R E, and the magnitude g of the acceleration due to gravity on the Earth's surface? A) B) C) v v 2 2 g R E = 9 = 2gR E D) v 2 = g R E 3 E) v 2 = g R E 4 v 2 = g R E A 0.75-kg ball is attached to a 1.0-m rope and whirled in a vertical circle. The rope will break when the tension exceeds 450 N. What is the maximum speed the ball can have at the bottom of the circle without breaking the rope? A) 24 m/s B) 12 m/s C) 32 m/s D) 16 m/s E) 38 m/s Page 22

23 81. The kinetic energy of an 1100-kg truck is J. What is the speed of the truck? A) 21 m/s B) 29 m/s C) 33 m/s D) 17 m/s E) 25 m/s 82. Two boxes are connected to each other as shown. The system is released from rest and the 1.00-kg box falls through a distance of 1.00 m. The surface of the table is frictionless. What is the kinetic energy of box B just before it reaches the floor? A) 2.45 J B) 4.90 J C) 9.80 J D) 29.4 J E) 39.2 J 83. The initial velocity of a 4.0-kg box is 11 m/s, due west. After the box slides 4.0 m horizontally, its speed is 1.5 m/s. Determine the magnitude and the direction of the nonconservative force acting on the box as it slides. A) 42 N, due west D) 59 N, due east B) 120 N, due east E) 83 N, due west C) 31 N, due east 84. A 40-kg block is lifted vertically 20 meters from the surface of the earth. To one significant figure, what is the change in the gravitational potential energy of the block? A) +800 J B) 800 J C) J D) 8000 J E) zero joules 85. A top fuel dragster with a mass of kg starts from rest and completes a quarter mile (402 m) race in a time of 5.0 s. The dragster's final speed is 130 m/s. Neglecting friction, what average power was needed to produce this final speed? A) 140 hp B) 750 hp C) 1100 hp D) hp E) hp 86. A 3.0-kg block falls from rest through a distance of 6.0 m in an evacuated tube near the surface of the earth. What is its speed after it has fallen the 6.0 m distance? Page 23

24 A) 8.0 m/s B) 11 m/s C) 13 m/s D) 26 m/s E) 120 m/s Use the following to answer question 87: A 2.0-kg projectile is fired with initial velocity components v ox = 30 m/s and v oy = 40 m/s from a point on the earth's surface. Neglect any effects due to air resistance. 87. How much work was done in firing the projectile? A) 900 J B) 1600 J C) 2500 J D) 4900 J E) 9800 J 88. A skier leaves the top of a slope with an initial speed of 5.0 m/s. Her speed at the bottom of the slope is 13 m/s. What is the height of the slope? A) 1.1 m B) 4.6 m C) 6.4 m D) 7.3 m E) 11 m 89. How much power is needed to lift a 75-kg student vertically upward at a constant speed of 0.33 m/s? A) 12.5 W B) 25 W C) 115 W D) 230 W E) 243 W 90. A concrete block is pulled 7.0 m across a frictionless surface by means of a rope. The tension in the rope is 40 N; and the net work done on the block is 247 J. What angle does the rope make with the horizontal? A) 28 B) 41 C) 47 D) 62 E) In which one of the following situations is zero net work done? A) A ball rolls down an inclined plane. B) A physics student stretches a spring. C) A projectile falls toward the surface of Earth. D) A box is pulled across a rough floor at constant velocity. E) A child pulls a wagon across a rough surface causing it to accelerate. 92. A 1500-kg car travels at a constant speed of 22 m/s around a circular track that is 80 m Page 24

25 across. What is the kinetic energy of the car? A) zero joules B) J C) J D) J E) J Use the following to answer question 93: A 300-N force accelerates a 50.0-kg crate from rest along a horizontal frictionless surface for a distance of 20.0 m as shown in the figure. 93. What coefficient of friction would be required to keep the crate moving at constant speed under the action of the 300-N force? A) 0.30 B) 0.32 C) 0.52 D) 0.61 E) How much energy is dissipated in braking a 1000-kg car to a stop from an initial speed of 20 m/s? A) J B) J C) J D) J E) J 95. A woman stands on the edge of a cliff and throws a stone vertically downward with an initial speed of 10 m/s. The instant before the stone hits the ground below, it has 450 J of kinetic energy. If she were to throw the stone horizontally outward from the cliff with the same initial speed of 10 m/s, how much kinetic energy would it have just before it hits the ground? A) 50 J B) 100 J C) 450 J D) 800 J E) 950 J Use the following to answer question 96: A rope exerts a force F on a 20.0-kg crate. The crate starts from rest and accelerates upward at 5.00 m/s 2 near the surface of the earth. Page 25

26 96. What is the kinetic energy of the crate when it is 4.0 m above the floor? A) 400 J B) 250 J C) 116 J D) 704 J E) 1180 J 97. The graph shows the force component along the displacement as a function of the magnitude of the displacement. Determine the work done by the force during the interval from 2 to 10 m. A) 140 J B) 190 J C) 270 D) 450 J E) 560 J 98. What power is needed to lift a 49-kg person a vertical distance of 5.0 m in 20.0 s? A) 12.5 W B) 25 W C) 60 W D) 120 W E) 210 W 99. Use the work-energy theorem to find the force required to accelerate an electron (m = kg) from rest to a speed of m/s in a distance of m. A) N D) N B) N E) N C) N Use the following to answer question 100: A 10.0-kg crate slides along a horizontal frictionless surface at a constant speed of 4.0 m/s. The crate then slides down a frictionless incline and across a second horizontal surface as shown in the figure. Page 26

27 100. What is the kinetic energy of the crate as it slides on the lower surface? A) 290 J B) 320 J C) 370 J D) 490 J E) 570 J Answer Key -- Sem1MC 1. D 2. E 3. D 4. B 5. B 6. D 7. D 8. E 9. D 10. B 11. C 12. B 13. B 14. B 15. C 16. A 17. E 18. E 19. E 20. C 21. A 22. D 23. D 24. E 25. A 26. B 27. C 28. C 29. B 30. E 31. B 32. E 33. B 34. D 35. A 36. C 37. E 38. B 39. E 40. A 41. D 42. E 43. A 44. C 45. D 46. B 47. B 48. C 49. D 50. B 51. D 52. B 53. E 54. C 55. B 56. A 57. A 58. E 59. B 60. E 61. A 62. A 63. C 64. D 65. C 66. D 67. E 68. E 69. D 70. A 71. B 72. B 73. C 74. C 75. B 76. E 77. C 78. E 79. C 80. A 81. B 82. A 83. D 84. C 85. C 86. B 87. C 88. D 89. E 90. A 91. D 92. B 93. D 94. B 95. C 96. A 97. B 98. D 99. A Page 27

28 100. C Page 28