Momentum Review 1 If Fast Freddy doubles his

Momentum Review

1. If Fast Freddy doubles his running speed, what else doubles A. B. C. D. His momentum His inertia His time of running His acceleration

2. A 3 -kg ball has the same speed as a 15 -kg ball. Compared with the 3 -kg ball, the 15 -kg ball has A. B. C. D. One-third the momentum The same momentum 3 times as much momentum 15 times as much momentum

3. The momentum of a 4 -kg dog running with a velocity of 1. 5 m/s is A. B. C. D. 6 m/s 2 2. 67 kg. m/s 6 kg. m/s 2. 67 N

4. If the mass of a cart full of groceries decreases to half and its speed doubles, the momentum of the cart A. B. C. D. Remains unchanged Is doubled Is quadrupled decreases

5. Your friend says the impulse equals momentum. You disagree and say the friend is missing an important word, which is A. B. C. D. inertia acceleration time change

6. The impulse-momentum relationship is a direct result of Newton’s A. B. C. D. First law Second law Third law Law of gravity

7. Which of the following equations best illustrates the usefulness of automobile air bags? A. B. C. D. a = F/m Ft = ∆mv d = ½ gt 2 d = vt

8. When you jump from an elevated position to the ground below, the force you experience when landing depends on A. B. C. D. The jumping height. The softness or hardness of the ground How much your keens bend All of the above

9. Standing on a skateboard, you toss a ball horizontally away from you. The mass of the ball is one-tenth your mass. Compared with the speed you give to the ball, your ideal recoil speed will be A. B. C. D. One-tenth as much The same Ten times as much One hundred times as much

10. A big fish swims upon and swallows a small fish at rest. After lunch, the momentum of the big fish is A. B. C. D. The same as before Less than before More than before zero

11. When both the force and time of contact are tripled, the impulse of an object is A. B. C. D. unchanged tripled 9 times more One-third

12. Imagine you are riding your bicycle and the brakes fail. You wisely choose to crash land in a large mass of bushes instead of on the asphalt road. This was a good decision because A. The landing will take longer in the bushes. B. You hit the bushes with more force than the asphalt C. you will not bounce off the bushes. D. None of the choices.

13. To increase the momentum of an object, you should A. Apply the smallest force you can and extend the time of application as much as possible. B. Apply the smallest force you can and shorten the time of application as much as possible. C. Apply the greatest force you can and extend the time of application as much as possible. D. Apply the greatest force you can and shorten the time of application as much as possible.

14. When a falling object hits the ground and then bounces, A. Its change in momentum is greater than for stopping the object. B. The impulse on it is greater than for stopping the object. C. Both of these D. None of these

15. Imagine that one ball hits another. The first ball comes to rest, while the second ball moves away with a velocity equal to the initial velocity of the first ball. What type of collision is this? A. An inelastic collision B. An elastic collision C. The answer depends on the mass of each ball. D. The answer depends on the initial velocity of the first ball.

16. A falling firecracker bursts into two pieces. Compared with the original momentum of the firecracker when it bursts, the two pieces A. B. C. D. Each have half the original momentum Each have one-quarter the original momentum. Combined have the same momentum Each have double the original momentum.

17. The momentum of a system may change if A. The mass of one object is significantly greater than the mass of the other. B. An inelastic collision occurs C. An external force is applied D. Two objects are moving in the same direction.

18. The more ______ an object has, the harder it is to stop. A. B. C. D. momentum Acceleration force All of the choices.

Answers 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. A C C A D B B D A a 11. C 12. A 13. C 14. C 15. B 16. C 17. C 18. a

Short Answer questions 1. In terms of impulse, why do air bags in cars reduce the chances of injury in accidents? 2. Differentiate between elastic and inelastic collisions. 3. In terms of impulse and momentum, why will a cannon with a long barrel fire a cannonball faster than the same cannon with a shorted barrel?

Calculations 1. What is the momentum of a 500 -kg car with a speed of 50 m/s?

2. Calculate the impulse on a cart if a force of 100 N is applied for 3 seconds.

3. A 1 -kg ostrich egg is thrown at 2 m/s at a bed-sheet and is brought to rest in 0. 2 s. What is the average amount of force applied?