Multiple Choice Practice

Transcription

1 Class: Date: Multiple Choice Practice Multiple Choice Identify the choice that best completes the statement or answers the question. 1. An ice skater moving at 10.0 m/s coasts to a halt in m on a smooth ice surface. What is the coefficient of friction between the ice and the skates? a c b d In the figure above, which diagram represents the vector addition C = A + B? a. I c. III b. II d. IV 3. A child on a sled slids down a hill starting at 20 m vertical distance up the hill. Disregarding friction, what is the velocity of the sled at the bottom of the hill? (g = 10 m/s 2.) a. 100 m/s c. 14 m/s b. 10 m/s d. 20 m/s 4. Disco Stu is hanging a 4.5 kg disco ball in his apartment with a piece of wire. What is the tension on the wire? a. 4.5 N c. 44 N b. 24 N d N 5. A track star in the long jump goes into the jump at 12 m/s and launches herself at 20.0 above the horizontal. What is the magnitude of her horizontal displacement? (Assume no air resistance and that a y = g = 9.81 m/s 2.) a. 4.6 m c. 13 m b. 9.2 m d. 15 m 6. A box weighing 210 N is pushed up an inclined plane that is 2.0 m long. A force of 140 N is required. If the box is lifted 1.0 m, what is the efficiency of the inclined plane? a. 33% c. 67% b. 50% d. 75% 13

2 7. O.J. Simpson escapes from jail and runs across the Nevada desert to escape from the police. He runs for 45 seconds at 5.6 m/s at 40 o North of East. He then changes direction and runs for 60 seconds at 5.0 m/s due north. What is the magnitude of his displacement? a. 552 m c. 462 m b. 500 m d. 250 m 8. A worker pushes a wheelbarrow with a horizontal force of 50.0 N over a level distance of 5.0 m. If a frictional force of 43 N acts on the wheelbarrow in a direction opposite to that of the worker, what net work is done on the wheelbarrow? a. 250 J c. 35 J b. 0.0 J d J 9. A sled weighs 100 N. It is held in place on a 30 slope by friction. Find the force of friction. 100 N Friction 30 a. 100 N b. 86 N c. 50 N d. 30 N e. 14 N 10. Harry Potter (55 kg) is on his magic broom and chasing the snitch at a constant velocity of 18 m/s straight up. He catches the snitch after going up 21 m. How much work did the broom do on Harry? a. 1.2 kj c. 200 J b kj d. 11 kj 11. A sled weighing N is held in place on a frictionless 20.0 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 c. 37 N b. 47 N d. 34 N 12. Two blocks, joined by a string, have masses of 6.0 and 9.0 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. 6kg 9kg a. 18 N b. 28 N c. 12 N d. 15 N e. 16 N 2

3 13. Which of the following statements does not describe force? a. Force causes objects at rest to remain stationary. b. Force causes objects to start moving. c. Force causes objects to stop moving. d. Force causes objects to change direction. 14. A 5-kilogram mass is lifted from the ground to a height of 10 meters. The gravitational potential energy of the mass is increased by approximately by how much. a. 0.5-J c. 250-J b. 50-J d. 500-J 15. What is the momentum of an asteroid that has a mass of kg and a velocity of m/s? a x kg m/s c x kg m/s b x kg m/s d x kg m/s 16. The figure shows a block that is being pulled along the floor. According to the figure, what is the acceleration of the block? 17. a. 2 m/s 2 c. 4 m/s 2 b. 3 m/s 2 d. 6 m/s 2 Two blocks, joined by a string, have masses of 6.0 and 9.0 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 6kg 9kg accelerate. Find the acceleration of blocks. a. 1 m/s 2 b. 2 m/s 2 c. 3 m/s 2 d. 5 m/s 2 e. 30 m/s How much elastic potential energy is stored in a bungee cord with a spring constant of 10.0 N/m when the cord is stretched 2.00 m? a J c J b J d. 200 J 3

4 19. In the graph above, how does the acceleration at A compare with the acceleration at B? a. The acceleration at A is positive and less than the acceleration at B. b. The acceleration at B is positive and less than the acceleration at A. c. The accelerations at A and B are each zero. d. The accelerations at A and B cannot be determined. 20. If constant force is applied perpendicular to an object s direction of motion, the object will a. speed up b. slow down c. move in a circular path at constant speed d. move in a parabolic path 21. If both the mass and the velocity of a ball are doubled, the kinetic energy of the ball is increased by a factor of a. 2. c. 4. b. 6. d A 1200-kg car experiences a a change in velocity of 5-m/s. If the applied force was 50-N, how long did the acceleration take? a. 1-minute c. 30 seconds b. 2-minutes d. 90 seconds 23. A missile is fired from rest into the air with a net force of 2000 N over a time period of 45 seconds. What is the momentum of the missile after the 45 seconds. a. 90,000 kg m/s c. 44 kg m/s b. 405,000 kg m/s d. 60,000 kg m/s 4

5 24. The diagram depicts a 2-kg mass colliding with and sticking to a second box. What is the mass of the second box? a. 4-kg c. 8-kg b. 6-kg d. 9-kg 25. Diomedes (98 kg) wants to launch himself over the walls of Troy with a giant slingshot. He has Achilles pull the slingshot back 2.5 m. Diomedes flys off of the slingshot with a velocity of 24 m/s. What is the spring constant for the slingshot? a. 6.0 x 10 3 N/m c. 1.8 x 10 4 N/m b. 2.3 x 10 4 N/m d. 9.0 x 10 3 N/m The figure above shows the path of a ball tossed from a building. Air resistance is ignored. 26. At what point of the ball s path shown in the figure above is the vertical component of the ball s velocity zero? a. A c. C b. B d. D 27. A sculpture is suspended in equilibrium by two cables, one from a wall and the other from the ceiling of a museum gallery. Cable 1 applies a horizontal force to the right of the sculpture and has a tension, F T1. Cable 2 applies a force upward and to the left at an angle of 37.0 to the negative x-axis and has a tension, F T2. The gravitational force on the sculpture is N. What is F T2? a N c N b N d N 5

6 28. Which of the following has the greatest momentum? a. truck with a mass of 2200 kg moving at a velocity of 30 m/s b. car with a mass of 1200 kg moving at a velocity of 50 m/s c. truck with a mass of 5000 kg moving at a velocity of 10 m/s d. car with a mass of 1000 kg moving at a velocity of 40 m/s 29. A roller coaster climbs up a hill at 4 m/s and then zips down the hill at 30 m/s. The momentum of the roller coaster a. is greater up the hill than down the hill. b. is greater down the hill than up the hill. c. remains the same throughout the ride. d. is zero throughout the ride. 30. Dwight drops a 4.4 kg watermelon off of a 25 m building. What is the kinetic energy of the watermelon right before it hits the ground? a. 110 J c J b J d J 31. Hercules throws a giant boulder with an initial velocity of 14.2 m/s at an angle of 28 o. It lands at the same height from which it was thrown. How far did Hercules throw the boulder? a. 17 m c. 4.8 m b. 34 m d. 52 m 32. 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? 30 a. 300 N b. 86 N c. 50 N d. 250 N e. 310 N 6

7 33. A ball rolls straight sideways off a 20m high building at a speed of 5 m/s. How far away from the edge does the ball land? V i 20 m x a. 20 m c. 5 m b. 10 m d. 2 m 34. Chanchito is pushing a 500. kg hot dog cart up a frictionless hill with a force of 1200 N. He pushes the cart a distance of 200. m. What is the angle of the hill? a. 14 degrees c. 8.2 degrees b. 30 degrees d. 42 degrees 35. Which of the following has the greatest power output? a. a weightlifter who lifts a 250 N weight 2.1 m in 3.0 s b. a mechanic s lift that raises a N car 2.1 m in 12 s c. a car engine that does J of work in 5.0 s d. a crane that lifts a N beam at a speed of 1.2 m/s 36. The magnitude of the gravitational force acting on an object is a. frictional force. c. inertia. b. weight. d. mass. 37. If a 3.0kg mass on the end of a pendulum is raised 4.5 m and given an initial velocity of 4.0 m/s, how high will the pendulum swing at the other end? v i = 4.0 m/s 4.5m 3 kg h f a. 16 m c. 5.0 m b. 4.5 m d. 9.0 m 38. A horizontal force of 200 N is applied to move a 55 kg television set across a 10 m level surface. What is the work done by the 200 N force on the television set? a. 550 J c J b J d J 7

8 39. Jimbo parks his 1200 kg car on a snowy hill with an angle of 35 o. The car does not slide down the hill. What is the minimum value for the coefficient of static friction between the tires and the snow? a c b. 1.3 d A 70-kg skier leaves a ski jump at a velocity of 14-m/s. What is the skier s momentum at that instant? a N s c. 490-N s b. 980-N s d. 5-N s 41. Three forces act on a mass as shown below, find the acceleration of the mass: 20 N 25 N 10 N 3 kg a. 5 m/s 2 d. 3 m/s 2 b. 15 m/s 2 e. 0.5 m/s 2 c m/s A net force of 6.8 N accelerates a 31 kg scooter across a level parking lot. What is the magnitude of the scooter s acceleration? a m/s 2 c. 3.2 m/s 2 b m/s 2 d. 4.6 m/s A ball is dropped from rest from a height 6.0 meters above the ground. The ball falls freely and reaches the ground 1.1 seconds later. What is the average speed of the ball? a. 5.5-m/s c. 6.6-m/s b. 6.1-m/s d. 11-m/s 44. How much time will it take for a person to walk the length of a football field (100 yards) at a constant speed of 5-ft/sec? a. 20 seconds c. 60 seconds b. 33 seconds d. 166 seconds 8

9 45. An object moves away from a motion detector with a constant speed. Which distance vs. time graph above best represents the motion of the object? a. A c. C b. B d. D 46. A toy car is given an initial velocity of 5.0 m/s and experiences a constant acceleration of 2.0 m/s 2. What is the final velocity after 6.0 s? a. 10 m/s d. 17 m/s b. 12 m/s e. 20 m/s c. 16 m/s 47. A race car accelerates from 0 m/s to 30.0 m/s in 5.00 seconds. What is the vehicle's displacement? a m d m b. 150 m e m c m 48. A 2 kg book sits on a table. What is the normal force? a. 2 N c. 20 N b. 10 N d. 18 N 9

10 49. A ball is thrown into the air with an intial speed of 20 m/s. What is the maximum height the ball will reach, measured from the point from which it was thrown? a. 20 m c. 4 m b. 10 m d. 40 m 50. If an object is launch from ground level with a vertical velocity of 30 m/s and a horizontal velocity of 20 m/s, find how far does the object travel in the air before hitting the ground. a. 20 m c. 60 m b. 90 m d. 120 m 51. A student holds a book at rest in an outstretched hand. The force exerted on the book by the student is equal to the book s a. mass. c. volume. b. weight. d. density. 52. A 50-kg child on a skateboard experiences a 75-N force as shown. What is the expected acceleration of the child? a m/s 2 c m/s 2 b m/s 2 d m/s 2 10

11 F a F n θ = 60 F k F g 53. In the diagram above, the crate has a weight of 10 N, the kinetic coefficient of friction is 0.50 and the applied force, at an angle of 60 below horizontal, equals 100 N. Calculate the net horizontal force acting on the crate. a N c. 3.4 N b. 6.8 N d. 1.7 N 11

12 F a F n F k F g 54. In the diagram above, the crate has a weight of 140 N, the kinetic coefficient of friction is 0.50 and the applied force has a horizontal component of 50 N and a vertical component of 87 N. Calculate the net horizontal acceleration acting on the crate. a. 23 m/s 2 c m/s 2 b. 2.3 m/s 2 d. 1.6 m/s Who won this 100-meter race? a. Albert c. Charlie b. Bob d. Not enough information. 12

13 56. By how many meters was the winner of the race in from of the second place finisher when he crossed the finish line? a. 2 c. 20 b. 10 d If the race were only 40-meters long, who would have been the winner? a. Albert c. Charlie b. Bob d. Not enough information. 58. A 2.0-kg mass is moving with a speed of 3.0-m/s. What is the kinetic energy of the mass? a. 1.5-J c. 9.0-J b. 6.0-J d J 59. The three objects above each move with a velocity of 1-m/s in the direction indicated. What is the total kinetic energy of the system? a. 1 c. 5 b. 2 d What is the kinetic energy of an object with a mass of 10 kilograms traveling at a speed of 10 meters per second? Assume no other forces act upon the object. a. 100-J c J b. 500-J d. 50,000-J 61. A 50-kilogram firefighter is on a ladder 10 meters above the ground. When the firefighter descends to 5 meters above the ground, the firefighter s gravitational potential energy will decrease by how much? a J c. 490-J b J d J 62. A hydraulic lift used at an automotive repair shop raises a 1000-kilogram car two meters off of the ground. What is the potential energy given to the car? a. 19,600-J c J b J d J 63. A 2.5-kg brick falls to the ground from a 3-m-high roof. What is the approximate kinetic energy of the brick just before it touches the ground? a. 75-J c. 12-J b. 38-J d. 11-J 13

14 64. When these two freight cars of different mass collide and couple, what will be their resultant velocity? a. 1-m/s c. 4-m/s b. 2-m/s d. 8-m/s 65. A force of 5-N is applied to an object for a time period of 6 seconds; what is the change in momentum for the object? a N s c. 30-N s b. 1.2-N s d. 90-N s 66. A 4-kg object initially traveling at 4-m/s slows to 8-m/s in a time period of 10 seconds. What was the applied force? a. 16-N c. 1.6-N b. 3.2-N d. 1.2-N 14