Physics! Review Problems Unit A force acting on a 7.0 kg body increases its speed uniformly from 1.0 m/s to 9.0 m/s in 3 s.

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1 Name Physics! Review Problems Unit 8 1. A force acting on a 7.0 kg body increases its speed uniformly from 1.0 m/s to 9.0 m/s in 3 s. a) What is the initial momentum of the body? b) What is the final momentum of the body? c) What is the force acting on it? 2. The driver of a 2500 kg car traveling at 10 m/s increases its speed to 50 m/s in 25 s. a) What is the change in momentum? b) What force is acting on the car? 3. A braking force is applied to a 300 kg motorcycle to reduce its speed from 20.0 m/s to 12.0 m/s in 20.0 s. a) What is the braking force? b) What is the acceleration?

2 4. How long must a 150 N force act on a 400 kg cart to raise its speed from 10 m/s to 22 m/s? 5. A shell having a mass of 45.0 kg is fired horizontally eastward from a cannon with a velocity of 700 m/s. If the mass of the cannon is 1000 kg, what is the recoil velocity of the cannon? 6. A bomb having a mass of 8 kg explodes into two pieces that fly out horizontally in opposite directions. One piece is found to have a mass of 6 kg and the other a mass of 2 kg. What was the ratio of the speed with which the two pieces moved apart after the explosion? 7. A toy railroad engine having a mass of 1.5 kg and moving on a straight track at 0.20 m/s collides with a similar engine ahead of it moving in the same direction at 0.12 m/s. On collision the engines lock and remain together. a) What was the momentum of each engine before the collision? b) What was the momentum of both engines after the collision? c) What is the velocity of the pair of engines after the collision?

3 8. When a car of mass 200 kg is moving at 9.0 m/s collides head on with a second car having a mass of 150 kg, the car lock and come to rest at the collision site. a) What was the momentum of the second car before the wreck? b) What was the velocity of the second car before the wreck? 9. A ball of mass 0.20 kg is pitched to a batter to 40 m/s and hit back toward the pitcher at 25 m/s. If the ball and bat were in contact for s... a) what force was exerted on the ball? b) what was the impulse? 10. A gun fires a 0.50 kg projectile which acquires a muzzle velocity of 500 m/s. If the projectile takes.005 s to travel the length of the gun barrel, what is the force exerted by the gun on the bullet while it is in the barrel? 11. What would the speed of the projectile in the previous problem be if the length of the barrel were increased so that the projectile took.012 s to travel the length of the barrel, but all other factors remained the same?

4 12. A 1 kg body moving forward at 5 m/s hits a second body at rest. After the collision, the 1 kg body reverses its direction and moves 1m/s while the second body moves forward at 2 m/s. a) What is the momentum of each body after the collision? b) What is the mass of the second body? 13. A 95-kg fullback, running at +8.2 m/s, collides in midair with a 128-kg defensive back moving in the opposite direction. The players both stop. Use the correct signs while calculating the following values. a) What is the fullback s momentum before the collision? b) What is the fullback s momentum after the collision? c) What is the fullback s change in momentum? d) What is the defensive back s change in momentum? e) What was the defensive back s velocity before the collision? 14. Glass ball A has a mass of 5.0-g and a velocity of cm/s. It collides with glass ball B that has a mass of 10.0-g and a velocity of cm/s along the same line. After the collision, A is still moving, but with a velocity of +8.0 cm/s. What is the velocity of B after the collision? 15. Before a collision, a 25-kg object is moving at m/s. Find the impulse that acted on the object if, after the collision, it has a velocity of: a) (+8.0 m/s) b) ( 8.0 m/s)

5 16. A 2575-kg van runs into the back of an 825-kg compact car at rest. They stick together and move off at 8.5 m/s. What was the initial velocity of the van? 17. A g bullet is shot into a 5085-g wooden block sitting on a table. Immediately after impact, the block, with the bullet imbedded in it, moves with a speed of 1.00 m/s. Calculate the velocity with which the bullet struck the block. 18. A hockey puck (m=0.115-kg) moving at 35.0 m/s strikes an octopus that was earlier thrown onto the ice by a fan. If the octopus has a mass of kg and is at rest when struck, find the speed with which the puck and octopus slide off together. 19. A 50.0-kg woman riding in a 10.0-kg cart is moving east at 5.00 m/s. The woman jumps out of the cart with a velocity of 7.00 m/s eastward relative to the ground. Calculate the velocity of the cart after she jumps out. 20. Two students on roller skates stand face-to-face and push each other away. One student has a mass of 93-kg and the other has a mass of 62-kg. a) Which student has the greater speed? b) Find the ratio of their velocities (V 93 : V 62 )

6 21. A 92-kg fullback, running at 5.0 m/s, attempts to dive across the goal line for a touchdown. Just as he reaches the goal line, he is met head-on in midair by two 75-kg linebackers, one moving at 2.0 m/s and the other at 4.0 m/s. If they all become entangled in one mass, does he move across the goal line or is he driven back? Show your work. 22. A cannon with a mass of 5100-kg fires a shell with a mass of 55-kg at a velocity of +150 m/s. What is the recoil velocity of the cannon? 23. Two campers dock their canoe. One camper steps out of the canoe onto the dock. This person has a mass of 80.0 kg and steps forward with a speed of 2.00 m/s. The other camper and canoe have a combined mass of 111 kg. With what speed with canoe move backward? 24. Analyze the graph to the right. A. Determine the impulse. B. If a 5 kg object which had an initial velocity of +3 m/s was subjected to this impulse, what would be the object s final velocity? 25. Analyze the graph to the right. A. Determine the impulse. B. If a 5 kg object which had an initial velocity of -3 m/s was subjected to this impulse, what would be the object s final velocity?