Ch 8 Momentum Test Review!

Transcription

1 Ch 8 Test Review! Multiple Choice Identify the choice that best completes the statement or answers the question. 1. The momentum of an object is defined as the object's a. mass times its velocity. b. force times the time interval. c. force times its acceleration. d. mass times its acceleration. e. velocity times the time interval. 2. Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour? a. Both have the same momentum. b. The small truck c. The large truck 3. Compared to a sports car moving at 30 miles per hour, the same sports car moving at 60 miles per hour has a. twice as much momentum. b. four times as much momentum. c. the same momentum. 4. If the momentum of an object changes and its mass remains constant, a. it is accelerating (or decelerating). b. there is a force acting on it. c. its velocity is changing. d. all of the above e. none of the above 5. The momentum change of an object is equal to the a. impulse acting on it. b. velocity change of the object. c. force acting on it. d. force acting on it times its velocity. e. object's mass times the force acting on it. 6. In order to increase the final momentum of a golf ball, we could a. increase the force acting on it. b. follow through when hitting the ball. c. increase the time of contact with the ball. d. swing as hard as possible. e. all of the above 7. The reason padded dashboards are used in cars is that they a. look nice and feel good. d. decrease the momentum of a collision. b. decrease the impulse in a collision. e. increase the time of impact in a collision. c. increase the force of impact in a collision. 8. A table tennis ball launcher is fired. Compared to the force on the ball, the force on the launcher is a. larger. b. the same. c. smaller. 9. A table tennis ball launcher is fired. Compared to the impulse on the ball, the impulse on the launcher is a. smaller. b. larger. c. the same. 10. of a system is conserved only when a. there are no internal forces acting on the system b. the system is not moving. 11. A collision is considered elastic if a. there is no lasting deformation. b. the objects don t stick together. c. the objects that collide don't get warmer. c. there are no forces acting on the system. d. no net external force acting on the system e. the system has zero momentum. d. after the collision, the objects have the same shape as before the collision. e. all of the above 12. Suppose a girl is standing on a pond where there is no friction between her feet and the ice. In order to get off the ice, she can a. bend over touching the ice in front of her and then bring her feet to her hands. b. walk very slowly on tiptoe. c. get on her hands and knees and crawl off the ice. d. throw something in the direction opposite to the way she wants to go. e. all of the above will work

2 13. Which of the following has the largest momentum? a. A large truck parked in a parking lot b. A tightrope walker crossing Niagara Falls c. The science building at your school d. A pickup truck traveling down the highway e. A dog running down the street 14. A freight train rolls along a track with considerable momentum. If it were to roll at the same speed but had twice as much mass, its momentum would be a. zero. b. unchanged. c. quadrupled. d. doubled. 15. A cannon recoils from launching a cannonball. The speed of the cannon's recoil is small because the a. impulse on the cannon is less than the impulse on the cannonball. b. cannon has far more mass than the cannonball. c. momentum of the cannon is unchanged. d. force against the cannon is relatively small. e. none of the above 16. Suppose a cannon is made of a strong but very light material. Suppose also that the cannonball is more massive than the cannon itself. For such a system a. conservation of momentum would not hold. d. the force on the cannonball would be greater b. conservation of energy would not hold. than the cannon. c. the target would be safer than the operator e. recoil problems would be lessened. 17. Two objects, A and B, have the same size and shape, but A is twice as heavy as B. When they are dropped simultaneously from a tower, they reach the ground at the same time, but A has a higher a. acceleration. b. momentum. c. speed. d. all of the above e. none of the above 18. In order to catch a ball, a baseball player moves his or her hand backward in the direction of the ball's motion. Doing this reduces the force of impact on the player's hand principally because a. the time of impact is decreased. d. the momentum of impact is reduced. b. the time of impact is increased. e. none of the above c. the velocity of the hand is reduced. 19. A car traveling along the highway needs a certain amount of force exerted on it to stop. More stopping force may be required when the car has a. less stopping distance. b. more momentum. c. more mass. d. all of the above e. none of the above 20. A cannon fires a cannonball. The speed of the cannonball will be the same as the speed of the recoiling cannon a. if the mass of the cannonball equals the mass d. because both velocity and momentum are of the cannon. conserved. b. because momentum is conserved. e. none of the above c. because velocity is conserved. 21. The force of an apple hitting the ground depends upon a. the speed of the apple just before it hits. b. the time of impact with the ground. c. whether or not the apple bounces. d. air resistance on the apple as it falls. e. all of the above 22. When you jump off a step, you usually bend your knees as you reach the ground. By doing this, the time of the impact is about 10 times more what it would be in a stiff-legged landing, and the average force on your body is reduced by a. less than 10 times. b. about 10 times. c. more than 10 times.

3 23. Recoil is noticeable if you throw a heavy ball while standing on roller skates. If instead you go through the motions of throwing the ball but hold onto it, your net recoil velocity will be a. small but noticeable. b. the same as before. c. zero. 24. A 1-N apple falls to the ground. The apple hits the ground with an impact force of a. 1 N. b. 2 N. c. 4 N. d. 9.8 N. e. Not enough information to say 25. A karate expert executes a swift blow and splits a cement block with her bare hand. a. The forces on both the block and the expert's hand have the same magnitude. b. The times of impact on both the block and the expert's hand are the same. c. The impulses on both the block and the expert's hand have the same magnitude. d. all of the above e. none of the above 26. A moving freight car runs into an identical car at rest on the track. The cars couple together. Compared to the velocity of the first car before the collision, the velocity of the combined cars after the collision is a. zero. b. one half as large. c. the same. d. twice as large 27. Two gliders having the same mass and speed move toward each other on an air track and stick together. After the collision, the velocity of the gliders is a. twice the original velocity. c. zero. b. one half the original velocity. d. the same as the original velocity. 28. The force that accelerates a rocket into outer space is exerted on the rocket by a. the exhaust gases. c. atmospheric pressure. b. Earth's gravity. d. rocket's wings. 29. If all people, animals, trains and trucks all over the world began to walk or run towards the east, then a. Earth would spin a bit slower. b. Earth's spin would not be affected at all. c. Earth would spin a bit faster. 30. Suppose an astronaut in outer space wishes to toss a ball against a very massive and perfectly elastic concrete wall and catch it as it bounces back. If the ball is as massive as the astronaut, then a. the astronaut's time between catches will decrease as the game progresses. b. the astronaut will never catch the first bounce. c. the astronaut will catch one bounce only. 31. Superman is at rest in space when he throws an asteroid that has more mass than he does. Which moves faster, Superman or the asteroid? a. Superman b. The asteroid c. They both move at the same speed. 32. A cannonball shot from a long-barrel cannon travels faster than one shot from a short-barrel cannon because the cannonball receives a greater a. force. b. impulse. c. both A and B d. neither A nor B 33. While roller-skating, Granny collides with her tiny grandson Ambrose who is at rest. Ignoring any friction effects, Ambrose's speed after the collision will be greatest when a. Granny catches him and they both move together. b. he and Granny make a bouncing collision, each going in opposite directions. 34. A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives the greater impulse is the a. limousine. b. small economy car. c. neither A nor B (same for each). 35. A piece of putty and a rubber ball have the same mass. If you drop them from the same height, which object will produce a greater impulse and why? a. The silly putty will produce a greater impulse because it will bounce.

4 b. The rubber ball will produce a greater impulse because it will bounce. c. The silly putty will produce a greater impulse because it will stop when it hits the ground. d. The rubber ball will produce a greater impulse because it will stop when it hits the ground. 36. A meteor that originally was heading south breaks up into two chunks. One of the chunks moves southwest. The second chunk was not immediately found, but scientists guessed that they should look for an object heading a. southeast b. northeast c. southwest d. northwest 37. A truck travels north with a momentum of 2,600 kg km/s, and a motorcycle heads west with a momentum of 1,500 kg km/s. The motorcycle hits the truck. If the two vehicles collide and then stick together, what is the momentum and direction of travel? a. The vehicles travel with a momentum of 3,000 kg km/s in the NW direction. b. The vehicles travel with a momentum of 6,000 kg km/s in the SW direction. c. The vehicles travel with a momentum of 3,000 kg km/s in the NW direction. d. The vehicles travel with a momentum of 6,000 kg km/s in the SW direction. True/False Indicate whether the statement is true or false. 38. is defined as an object's mass times its velocity. 39. Impulse is defined as the force exerted on an object times the time it lasts. 40. If the net external force acting on a system is zero, then the total momentum of the system is zero. 41. When two objects collide and completely bounce apart with no lasting deformation or generation of heat, the collision is said to be elastic. 42. When two objects collide and stick together, the collision is said to be inelastic. 43. Impulses are normally smaller when bouncing takes place. 44. Perfectly elastic collisions between large objects are uncommon in the everyday world. 45. When a baseball player follows through in hitting the ball, the contact time with the ball is longer. 46. Automobile dashboards that are padded lengthen the time of impact in case of a collision. 47. If a net force acts on a system, the system's momentum will change. 48. is a scalar quantity. 49. is NOT conserved when interacting objects don t move along the same straight line. Problem (SHOW ALL WORK) 50. What is the average momentum of a 50-kg skateboarder who covers 400 m in 50 s? 51. A cement truck of mass 16,000 kg moving at 15 m/s slams into a cement wall and comes to a halt. What was the truck s change in momentum?

5 52. A 10-kg cement block moving horizontally at 6 m/s plows into a bank of sand and comes to a stop in 2 s. What is the average impact force on the bank? 53. An 8-kg blob of clay moving horizontally at 2 m/s hits a 3-kg blob of clay at rest. What is the speed of the two blobs stuck together immediately after the collision? 54. A 40-kg football player leaps through the air to collide with and tackle a 50-kg player heading toward him, also in the air. If the 40-kg player is heading to the right at 9 m/s and the 50-kg player is heading toward the left at 2 m/s, what is the speed and direction of the tangled players? 55. A 5-kg blob of clay moving horizontally at 4 m/s has a head-on collision with a 4-kg blob of clay that moves toward it at 2 m/s. What is the speed of the two blobs stuck together immediately after the collision? 56. A 10-kg bowling ball moving at 4 m/s bounces off a spring at about the same speed that it had before bouncing. What is the change in momentum of the bowling ball? 57. A loaded freight car has 5 times as much mass as an empty freight car. If the loaded car coasts at 5 m/s and collides with and attaches to the empty car at rest, what will be the speed of both cars after collision? 58. A 50-kg cart moving at 100 km/h collides head-on with an approaching 50-kg cart moving at 10 km/h (in the opposite direction). If the two carts stick together, what will be their speed? 59. A 30-kg girl and a 50-kg boy face each other on friction-free roller skates. The girl pushes the boy, who moves away at a speed of 3 m/s. What is the girl's speed? 60. Assume that a 15-kg ball moving at 8 m/s strikes a wall perpendicularly and rebounds elastically at the same speed. What is the amount of impulse given to the wall?

6 Ch 8 Test Review! Answer Section MULTIPLE CHOICE 1. ANS: A PTS: 1 DIF: L1 OBJ: 8.1 STA: Ph.2.d KEY: momentum mass BLM: knowledge 2. ANS: C PTS: 1 DIF: L2 OBJ: 8.1 STA: Ph.2.d KEY: momentum mass 3. ANS: A PTS: 1 DIF: L2 OBJ: 8.1 STA: Ph.2.d KEY: momentum mass 4. ANS: D PTS: 1 DIF: L2 OBJ: 8.1 STA: Ph.2.d KEY: momentum velocity mass 5. ANS: A PTS: 1 DIF: L1 OBJ: 8.2 Impulse Changes KEY: momentum impulse BLM: knowledge 6. ANS: E PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: momentum force 7. ANS: E PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: impact time BLM: application 8. ANS: B PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: force 9. ANS: C PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: impulse 10. ANS: D PTS: 1 DIF: L1 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: momentum conserve BLM: knowledge 11. ANS: E STA: Ph.2.g KEY: collision elastic 12. ANS: D PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: opposite force 13. ANS: D PTS: 1 DIF: L2 OBJ: 8.1 STA: Ph.2.d KEY: momentum 14. ANS: D PTS: 1 DIF: L2 OBJ: 8.1 STA: Ph.2.d KEY: momentum mass 15. ANS: B PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: recoil mass 16. ANS: C PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: mass recoil BLM: application 17. ANS: B PTS: 1 DIF: L2 OBJ: 8.1 STA: Ph.2.d KEY: momentum weight 18. ANS: B PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: impact momentum 19. ANS: D PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: force stop 20. ANS: A PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: speed cannon mass 21. ANS: E PTS: 1 DIF: L2 OBJ: 8.3 Bouncing

7 STA: Ph.2.g KEY: force impact BLM: analysis 22. ANS: B PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: force impact 23. ANS: C PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: recoil velocity 24. ANS: A PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: force BLM: application 25. ANS: D STA: Ph.2.g KEY: impulse impact magnitude 26. ANS: B STA: Ph.2.g KEY: velocity collision 27. ANS: C STA: Ph.2.g KEY: collision velocity BLM: application 28. ANS: A PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: force acceleration 29. ANS: A PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: Earth spin BLM: analysis 30. ANS: B PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: elastic mass BLM: application 31. ANS: A PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: speed force 32. ANS: B PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: impulse cannon 33. ANS: B STA: Ph.2.g KEY: rest collision 34. ANS: A PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: mass force impulse 35. ANS: B PTS: 1 DIF: L2 OBJ: 8.3 Bouncing STA: Ph.2.g KEY: bouncing impulse BLM: application 36. ANS: A PTS: 1 DIF: L2 OBJ: 8.6 Vectors KEY: momentum vectors BLM: application 37. ANS: A PTS: 1 DIF: L2 OBJ: 8.6 Vectors KEY: momentum vectors BLM: application TRUE/FALSE 38. ANS: T PTS: 1 DIF: L1 OBJ: 8.1 STA: Ph.2.d KEY: momentum mass BLM: knowledge 39. ANS: T PTS: 1 DIF: L1 OBJ: 8.2 Impulse Changes KEY: impulse time BLM: knowledge 40. ANS: F PTS: 1 DIF: L1 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: net force momentum BLM: knowledge 41. ANS: T PTS: 1 DIF: L1 OBJ: 8.5 Collisions

8 STA: Ph.2.g KEY: collision elastic BLM: knowledge 42. ANS: T PTS: 1 DIF: L1 OBJ: 8.5 Collisions STA: Ph.2.g KEY: collision elastic BLM: knowledge 43. ANS: F PTS: 1 DIF: L1 OBJ: 8.3 Bouncing STA: Ph.2.g KEY: impulse bounce BLM: knowledge 44. ANS: T PTS: 1 DIF: L1 OBJ: 8.5 Collisions STA: Ph.2.g KEY: collision elastic BLM: knowledge 45. ANS: T PTS: 1 DIF: L1 OBJ: 8.2 Impulse Changes KEY: force time BLM: knowledge 46. ANS: T PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: impact time 47. ANS: T PTS: 1 DIF: L1 OBJ: 8.2 Impulse Changes KEY: net force momentum BLM: knowledge 48. ANS: F PTS: 1 DIF: L1 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: momentum scalar BLM: knowledge 49. ANS: F PTS: 1 DIF: L1 OBJ: 8.6 Vectors KEY: momentum vectors BLM: knowledge PROBLEM 50. ANS: 400 kg m/s PTS: 1 DIF: L2 OBJ: 8.1 STA: Ph.2.d KEY: momentum BLM: application 51. ANS: Not enough information to say. PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: impact BLM: application 52. ANS: 30 N PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: force BLM: application 53. ANS: 1.5 m/s STA: Ph.2.g KEY: speed collision BLM: application 54. ANS: 2.9 m/s toward the right STA: Ph.2.g KEY: speed direction BLM: application 55. ANS: 1.3 m/s STA: Ph.2.g KEY: speed collision BLM: application

9 56. ANS: 80 kg m/s PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: speed momentum BLM: application 57. ANS: 4.2 m/s STA: Ph.2.g KEY: mass collision BLM: application 58. ANS: 45.0 km/h STA: Ph.2.g KEY: speed collision BLM: application 59. ANS: 5.0 m/s PTS: 1 DIF: L2 OBJ: 8.4 Conservation of STA: Ph.2.e KEY: speed BLM: application 60. ANS: 240 N s PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes KEY: elastic speed BLM: application