1. A 0.16 kg baseball thrown at 40 m/s is hit directly bak in the opposite direction at 55 m/s.

a. What is the impulse imparted to the ball by the bat?

b. If the ball and bat are in contact for 2x10^-3 seconds, what is the average force of the bat on the ball?

2. An impulse of 150 Ns is required to stop a person's head in a car collision. If the face is in contact with the steeling wheel for .02 seconds:

a. What is the force on the cheekbone?

b. If 900 N fractures the cheekbone, how long will it be in contact with the steering wheel in order to fracture?

3. A .06 kg tennis ball strikes a racket at 10 m/s and rebounds in the opposite direction at 20 m/s. If it is in contact for .01 seconds, what is the average force of the racket on the ball?

4. A cheekbone will fracture if subjected to 900 N of force lasting 6 ms or longer.

a. What change in velocity is needed for a .11 kg hockey puck to provide this force?

b. If a goalie's face mask doubles the impact time, by how much does this change the force?

5. An 80 kg person is standing stiff-legged in a free falling elevator. The elevator strikes a shock absorber traveling at 20 m/s. In order to avoid injury, the person should not experience more than 4x10^4 N. What is the minimum stopping time and distance to save this poor soul?