Physics
Vandebilt Catholic High School
W. Dupre

                                                                                                       

MOMENTUM -  GUIDE

 

For the test know all the material covered in this chapter and know how to solve problems using the impulse - momentum change relationship and the Law of Conservation of Momentum.

 

Some extra questions to be aware of!!

 

1.       What is meant by an isolated system?

 

2.     The white cue ball travels across the table and collides into the stationary eight ball of equal mass. After the collision the cue ball is at rest. What must be true of the speed of the eight ball?

 

3.      Consider a falling ball. Define a system in which the total momentum is conserved.

 

4.     During a space walk, the tether connecting the astronaut to the space capsule breaks. Explain how the astronaut can use his gas pistol to safely return to the capsule.

 

5.      Two trucks that look the same collide. One was originally at rest. The trucks stick together and move off at more than half the original speed of the moving truck. What can you say about the contents of the two trucks?

 

6.     Two bullets of equal mass are shot at equal speeds at blocks of wood on a frictionless surface. One bullet, made of rubber, bounces off the wood. The other bullet, made of aluminum, penetrates into the wood. Which bullet makes the wood move faster? Why?

 

7.     Which collision represents the greatest possible danger to the passengers involved: (1) two cars colliding and remaining entangled, or (2) the same two cars colliding and rebounding off each other? Explain.

 

8.     If the kinetic energy of a particle is zero, what is its momentum? If the total energy of a particle is zero, is its momentum necessarily zero? Explain.

 

9.     If the velocity of a particle is doubled, by what factor is its momentum changed? What happens to its kinetic energy?

 

10.  If two particles have equal kinetic energies, are their momenta necessarily equal? Explain or give an example.

 

11.    Does a large force always produce a larger impulse on a body than a smaller force? Explain.

 

12.  If two objects collide and one is initially at rest, is it possible for both to be at rest after the collision? Is it possible for one to be at rest after the collision? Explain.

 

13.   Will a Mac truck always have more momentum than a roller skate? Explain.

 

14.  When a ball rolls down an incline, its momentum in creases. Does this imply that momentum is not con served? Explain.

 

15.   A boy stands at one end of a floating raft that is stationary relative to the shore. He then walks to the opposite end of the raft, away from the shore. What happens to the center of mass of the system (boy + raft)? Describe the movement of the raft.

 

16.  A sharpshooter fires a rifle while standing with the butt of the gun against his shoulder. If the forward momentum of a bullet is the same as the backward momentum of the gun, why isn’t it as dangerous to be hit by the gun as by the bullet?

 

17.  A pole vaulter falls from a height of 15 ft onto a foam rubber pad. Could you calculate his velocity just be fore he reaches the pad? Would you be able to calculate the force exerted on him due to the collision? Explain.

 

18.   A man is at rest sitting at one end of a boat in the middle of a lake. If he walks to the opposite end of the boat toward the east, why does the boat move west?

 

19.  Explain how you would use a balloon to demonstrate the mechanism responsible for rocket propulsion.

 

20. A ball is dropped from a tall building in New York. Identify the system whose momentum is conserved.

 

21.  A bomb, initially at rest, explodes into several pieces. In this process is the  momentum conserved? Explain.

 

22. A skaters standing still on a frictionless ice rink. Her friend throws a Frisbee straight at her. In which of the following cases is the largest momentum transferred to the skater? (a) The skater catches the Frisbee and holds it, (b) catches it momentarily but drops it vertically down, (c) catches the Frisbee momentarily and then throws it back to her friend.

 

23. A large sheet is held at its edges by two students in such a way that it forms a nearly vertical net to catch an object. A third student, who happens to be the star pitcher on the baseball team, is asked to throw a raw egg into the sheet. Explain why the egg does not break in the process, regardless of the initial speed of the egg.

 

24.How does "follow through" increase our proficiency in certain activities such as baseball, golf, boxing, tennis, etc.

 

25. Explain how the impulse-momentum relationship may allow for an individual to fall from a three story building without serious injury.

 

26.  Theoretically, would it be less harmful to be running in the same direction as a golf ball that is about to strike you in the head or to be running in the opposite direction of the golf ball? Explain.

 

27.  Distinguish between elastic and inelastic collisions.

 

28.What is the relationship between impulse and momentum.

 

29. a) When you ride a bike at full speed, which has the greater momentum - you are the bike?   b) Does this help explain why you go over the handlebars if the bike is brought to a sudden halt?

 

30. Why will you be hurt less if you fall on a floor with "give" instead of a rigid one.