1. Conservation of Energy

2. Conservative Force One for which work done does not depend on the path taken only on initial and final positions Gravity and elastic forces are conservative Why is kinetic energy not conservative?

3. If No Non-Conservative Forces Total work is the same before and after a change KE 1 + PE 1 = KE 2 + PE 2

4. Conservation of Mechanical Energy If only conservative forces act, the total mechanical energy in a system neither increases nor decreases

5. Ex. 1 If a stone is dropped from a height of 3.0m, what is the stone’s speed when it has fallen to 1.0m?

6. Ex. 2 A roller coaster car starts at the top of a 40m high hill a) find the speed of the car at the bottom of the hill b) at what height will it have half of this speed?

7. Ex. 3 What is the kinetic energy and speed required for a 70kg pole vaulter to just pass over a 5.0m high bar? The vaulter’s center of mass is.90m off the ground.

8. Ex. 4 A dart gun of.100kg is pressed against the spring of a toy dart gun. The spring (k = 250 N/m) is compressed 6.0cm and released. What speed does the dart acquire?