Chapter 6: Momentum and Collisions

Transcription

1 Assumption College English Program Mr. Stephen Dobosh s EP- M 4 P h y s i c s C l a s s w o r k / H o m e w o r k P a c k e t Chapter 6: Momentum and Collisions Section 1: Momentum and Impulse Section 2: Conservation of Momentum Section 3: Elastic and Inelastic Collisions Student s Name.... EP-M./. ID #.. Register # Much of the material within this packet is drawn from the course textbook Holt Physics that each of you have purchased. This content is copyrighted 2012 by Holt McDougal, a division of Houghton Mifflin Harcourt Publishing Company. No part of this work may be reproduced or transmitted in any form without prior written permission of the copyright owner.

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3 Mr. Stephen Dobosh Page 3 of 25 Summary table of Types of Collisions. See p EQUATION SHEET

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5 Mr. Stephen Dobosh Page 5 of 25 Chapter 6.1: Momentum and Impulse (pp ) Practice A, p. 191 #1-3 Momentum Due: 1. A deer with a mass of 146 kg is running head-on toward you with a speed of 17 m/s. You are going north. Find the momentum of the deer. 2. A 21 kg child on a 5.9 kg bike is riding with a velocity of 4.5 m/s to the northwest. a. What is the total momentum of the child and the bike together? b. What is the momentum of the child? c. What is the momentum of the bike? 3. What velocity must a 1210 kg car have in order to have the same momentum as the pickup truck in Sample Problem A?

6 Mr. Stephen Dobosh Page 6 of 25 Chapter 6.1: Momentum and Impulse (pp ) Practice B, p. 193 #1-4 Force and Impulse Due: 1. A 0.50 kg football is thrown with a velocity of 15 m/s to the right. A stationary receiver catches the ball and brings it to rest in s. What is the force exerted on the ball by the receiver? 2. An 82 kg man drops from rest on a diving board 3.0 m above the surface of the water and comes to rest 0.55 s after reaching the water. What is the net force on the diver as he is brought to rest? 3. A 0.40 kg soccer ball approaches a player horizontally with a velocity of 18 m/s to the north. The player strikes the ball and causes it to move in the opposite direction with a velocity of 22 m/s. What impulse was delivered to the ball by the player? 4. A 0.50 kg object is at rest. A 3.00 N force to the right acts on the object during a time interval of 1.50 s. a. What is the velocity of the object at the end of this interval? b. At the end of this interval, a constant force of 4.00 N to the left is applied for 3.00 s. What is the velocity at the end of the 3.00 s?

7 Mr. Stephen Dobosh Page 7 of 25 Chapter 6.1: Momentum and Impulse (pp ) Practice C, pp #1-3 Stopping Distance Due: 1. How long would the car in Sample Problem C take to come to a stop from its initial velocity of 20.0 m/s to the west? How far would the car move before stopping? Assume a constant acceleration. 2. A 2500 kg car traveling to the north is slowed down uniformly from an initial velocity of 20.0 m/s by a 6250 N braking force acting opposite the car s motion. Use the impulse-momentum theorem to answer the following questions: a. What is the car s velocity after 2.50 s? b. How far does the car move during 2.50 s? c. How long does it take the car to come to a complete stop? 3. Assume that the car in Sample Problem C has a mass of 3250 kg. a. How much force would be required to cause the same acceleration as in item 1? Use the impulse-momentum theorem. b. How far would the car move before stopping? (Use the force found in a.)

8 Mr. Stephen Dobosh Page 8 of 25 Chapter 6.1: Momentum and Impulse (pp ) Formative Assessment 6.1, p. 196 #1-5 Due: 1. The speed of a particle is doubled. a. By what factor is its momentum changed? b. What happens to its kinetic energy? 2. A pitcher claims he can throw a kg baseball with as much momentum as a speeding bullet. Assume that a 3.00 g bullet moves at a speed of m/s. a. What must the baseball s speed be if the pitcher s claim is valid? b. Which has greater kinetic energy, the ball or the bullet? 3. A 0.42 kg soccer ball is moving downfield with a velocity of 12 m/s. A player kicks the ball so that it has a final velocity of 18 m/s downfield. a. What is the change in the ball s momentum? b. Find the constant force exerted by the player s foot on the ball if the two are in contact for s. 4. Critical Thinking When a force is exerted on an object, does a large force always produce a larger change in the object s momentum than a smaller force does? Explain. 5. Critical Thinking What is the relationship between impulse and momentum?

9 Mr. Stephen Dobosh Page 9 of 25 Chapter 6.2: Conservation of Momentum (pp ) Practice D, pp #1-4 Conservation of Momentum Due: 1. A 63.0 kg astronaut is on a spacewalk when the tether line to the shuttle breaks. The astronaut is able to throw a spare 10.0 kg oxygen tank in a direction away from the shuttle with a speed of 12.0 m/s, propelling the astronaut back to the shuttle. Assuming that the astronaut starts from rest with respect to the shuttle, find the astronaut s final speed with respect to the shuttle after the tank is thrown. 2. An 85.0 kg fisherman jumps from a dock into a kg rowboat at rest on the west side of the dock. If the velocity of the fisherman is 4.30 m/s to the west as he leaves the dock, what is the final velocity of the fisherman and the boat? 3. Each croquet ball in a set has a mass of 0.50 kg. The green ball, traveling at 12.0 m/s, strikes the blue ball, which is at rest. Assuming that the balls slide on a frictionless surface and all collisions are head-on, find the final speed of the blue ball in each of the following situations: a. The green ball stops moving after it strikes the blue ball. b. The green ball continues moving after the collision at 2.4 m/s in the same direction. 4. A boy on a 2.0 kg skateboard initially at rest tosses an 8.0 kg jug of water in the forward direction. If the jug has a speed of 3.0 m/s relative to the ground and the boy and skateboard move in the opposite direction at 0.60 m/s, find the boy s mass.

10 Mr. Stephen Dobosh Page 10 of 25 Chapter 6.2: Conservation of Momentum (pp ) Formative Assessment 6.2, p. 203 #1-4 Due: 1. A 44 kg student on in-line skates is playing with a 22 kg exercise ball. Disregarding friction, explain what happens during the following situations. In (a), calculate the ball s speed. a. The student is holding the ball, and both are at rest. The student then throws the ball horizontally, causing the student to glide back at 3.5 m/s. b. Explain what happens to the ball in part (a) in terms of the momentum of the student and the momentum of the ball. In (c), calculate the combined speed. c. The student is initially at rest. The student then catches the ball, which is initially moving to the right at 4.6 m/s. d. Explain what happens in part (c) in terms of the momentum of the student and the momentum of the ball. 2. A boy stands at one end of a floating raft that is stationary relative to the shore. He then walks in a straight line to the opposite end of the raft, away from the shore. a. Does the raft move? Explain. b. What is the total momentum of the boy and the raft before the boy walks across the raft? c. What is the total momentum of the boy and the raft after the boy walks across the raft?

11 Mr. Stephen Dobosh Page 11 of High-speed stroboscopic photographs show the head of a 215 g golf club traveling at 55.0 m/s just before it strikes a 46 g golf ball at rest on a tee. After the collision, the club travels (in the same direction) at 42.0 m/s. Use the law of conservation of momentum to find the speed of the golf ball just after impact. 4. Critical Thinking Two isolated objects have a head-on collision. For each of the following questions, explain your answer. Hint: Look back at our class notes. Reference the equations. Look at the variables and you ll be able to see what you can and cannot find in each situation. a. If you know the change in momentum of one object, can you find the change in momentum of the other object? b. If you know the initial and final velocity of one object and the mass of the other object, do you have enough information to find the final velocity of the second object? c. If you know the masses of both objects and the final velocities of both objects, do you have enough information to find the initial velocities of both objects? d. If you know the masses and initial velocities of both objects and the final velocity of one object, do you have enough information to find the final velocity of the other object? e. If you know the change in momentum of one object and the initial and final velocities of the other object, do you have enough information to find the mass of either object?

12 Mr. Stephen Dobosh Page 12 of 25 Chapter 6.3: Elastic and Inelastic Collisions (pp ) Practice E, pp #1-5 Perfectly Inelastic Collisions Due: 1. A 1500 kg car traveling at 15.0 m/s to the south collides with a 4500 kg truck that is initially at rest at a stoplight. The car and truck stick together and move together after the collision. What is the final velocity of the two-vehicle mass? 2. A grocery shopper tosses a 9.0 kg bag of rice into a stationary 18.0 kg grocery cart. The bag hits the cart with a horizontal speed of 5.5 m/s toward the front of the cart. What is the final speed of the cart and bag? 3. A kg railroad car moving at 7.00 m/s to the north collides with and sticks to another railroad car of the same mass that is moving in the same direction at 1.50 m/s. What is the velocity of the joined cars after the collision? 4. A dry cleaner throws a 22 kg bag of laundry onto a stationary 9.0 kg cart. The cart and laundry bag begin moving at 3.0 m/s to the right. Find the velocity of the laundry bag before the collision. 5. A 47.4 kg student runs down the sidewalk and jumps with a horizontal speed of 4.20 m/s onto a stationary skateboard. The student and skateboard move down the sidewalk with a speed of 3.95 m/s. Find the following: a. the mass of the skateboard b. how fast the student would have to jump to have a final speed of 5.00 m/s

13 Mr. Stephen Dobosh Page 13 of 25 Chapter 6.3: Elastic and Inelastic Collisions (pp ) Practice F, pp #1-5 Kinetic Energy in Perfectly Inelastic Collisions Due: 1. A 0.25 kg arrow with a velocity of 12 m/s to the west strikes and pierces the center of a 6.8 kg target. a. What is the final velocity of the combined mass? b. What is the decrease in kinetic energy during the collision? 2. During practice, a student kicks a 0.40 kg soccer ball with a velocity of 8.5 m/s to the south into a 0.15 kg bucket lying on its side. The bucket travels with the ball after the collision. a. What is the final velocity of the combined mass? b. What is the decrease in kinetic energy during the collision? 3. A 56 kg ice skater traveling at 4.0 m/s to the north meets and joins hands with a 65 kg skater traveling at 12.0 m/s in the opposite direction. Without rotating, the two skaters continue skating together with joined hands. a. What is the final velocity of the two skaters? b. What is the decrease in kinetic energy during the collision?

14 Mr. Stephen Dobosh Page 14 of 25 Chapter 6.3: Elastic and Inelastic Collisions (pp ) Practice G, pp #1-4 Elastic Collisions Due: 1. A kg marble sliding to the right at 22.5 cm/s on a frictionless surface makes an elastic head-on collision with a kg marble moving to the left at 18.0 cm/s. After the collision, the first marble moves to the left at 18.0 cm/s. a. Find the velocity of the second marble after the collision. b. Verify your answer by calculating the total kinetic energy before and after the collision. 2. A 16.0 kg canoe moving to the left at 12.5 m/s makes an elastic head-on collision with a 14.0 kg raft moving to the right at 16.0 m/s. After the collision, the raft moves to the left at 14.4 m/s. Disregard any effects of the water. a. Find the velocity of the canoe after the collision. b. Verify your answer by calculating the total kinetic energy before and after the collision.

15 Mr. Stephen Dobosh Page 15 of A 4.0 kg bowling ball sliding to the right at 8.0 m/s has an elastic head-on collision with another 4.0 kg bowling ball initially at rest. The first ball stops after the collision. a. Find the velocity of the second ball after the collision. b. Verify your answer by calculating the total kinetic energy before and after the collision. 4. A 25.0 kg bumper car moving to the right at 5.00 m/s overtakes and collides elastically with a 35.0 kg bumper car moving to the right. After the collision, the 25.0 kg bumper car slows to 1.50 m/s to the right, and the 35.0 kg car moves at 4.50 m/s to the right. a. Find the velocity of the 35 kg bumper car before the collision. b. Verify your answer by calculating the total kinetic energy before and after the collision.

16 Mr. Stephen Dobosh Page 16 of 25 Chapter 6.3: Elastic and Inelastic Collisions (pp ) Formative Assessment 6.3, p. 212 #1-5 Due: 1. Give two examples of elastic collisions and two examples of perfectly inelastic collisions. 2. A 95.0 kg fullback moving south with a speed of 5.0 m/s has a perfectly inelastic collision with a 90.0 kg opponent running north at 3.0 m/s. a. Calculate the velocity of the players just after the tackle. b. Calculate the decrease in total kinetic energy as a result of the collision. 3. Two 0.40 kg soccer balls collide elastically in a head-on collision. The first ball starts at rest, and the second ball has a speed of 3.5 m/s. After the collision, the second ball is at rest. a. What is the final speed of the first ball? b. What is the kinetic energy of the first ball before the collision? c. What is the kinetic energy of the second ball after the collision?

17 Mr. Stephen Dobosh Page 17 of Critical Thinking If two automobiles collide, they usually do not stick together. Does this mean the collision is elastic? 5. Critical Thinking A rubber ball collides elastically with the sidewalk. a. Does each object have the same kinetic energy after the collision as it had before the collision? Explain. b. Does each object have the same momentum after the collision as it had before the collision? Explain.

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