Work out the following problems. Be sure to show your work in detail. See the “Module 3 Handout” for examples of how the problems should be solved and presented.

(Problems revised September 2012).

1. An electric motor performs 2000 J of work while lifting a 50 kg mass. How far does it lift the mass? (Assume Earth-standard gravity.) It it takes the motor 10 seconds to accomplish this action, what is its power?

2. What is the KE (in J) of a 12 g .45 ACP bullet with a muzzle velocity of 300 m/s? What is its momentum?

3. A standard baseball weights 145 g. If it is thrown vertically with an initial velocity of 60 mph, what is its potential energy change at its highest point? How high does the baseball rise? Neglect air friction.

4. Consider the surface of a pool table to be a closed system. A cue ball traveling at 2 m/s hits the eight ball. The cue ball stops dead, and the eight ball rolls away at 2 m/s. After colliding with other balls and the bumpers, the eight ball finally stops. At what point, in this scenario, is momentum conserved? At what point is energy conserved? Be specific.

5. A 1200 kg Honda Civic traveling at 100 km/hr on a country road hits a 120 kg deer that’s standing motionless in the middle of the lane. The deer and windshield wind up in the front seat. What is the velocity of the car + deer system in the moment immediately following the collision? (Assume no brakes were applied, there was no friction, etc. — that is, all the typically unrealistic Physics I assumptions.)