1. Conservation of Energy Aim: How does energy transfer from one form to another?

2. Types of Energy Potential Energy Kinetic Energy INTERNAL Energy (HEAT) Electromagnetic Energy (LIGHT) Sound Energy Electric Energy Chemical Energy Electrochemical Energy (BATTERIES) Nuclear Energy Total Mechanical Energy = PE + KE

3. Law of Conservation of Energy The energy in a closed system is neither created nor destroyed but changes from one form to another; the energy at the BEGINNING of the event is equal to the energy at the END of the event Total Energy Units: (J) Potential Energy Units: (J) Kinetic Energy Units: (J) Internal Energy [Requires Friction] Units: (J)

4. Example #1 Starting from rest, an 80kg skier goes down a 20m frictionless slope. (a) How much kinetic energy will he have at the bottom of the slope? (b) How fast will he be going? 20m

5. Example #2 The combined mass of a child on a pogo-stick is 50kg. If the pogo-stick has a spring constant of 40,000N/m and is compressed 10cm, how high will the child go? Assume no friction

6. Example #3 A 2000kg rollercoaster car starts 30m (A) above the ground and is travelling at 2m/s on a frictionless track. How fast will the car go when it reaches the 15m tall hill (B)? A B

7. Example #3 A 2000kg rollercoaster car starts 30m (A) above the ground and is travelling at 2m/s on a frictionless track. How fast will the car go when it reaches the 15m tall hill (B)? A B

8. Example #4 A 160g puck has an initial velocity of 7.7m/s. If the puck comes to a stop after 20m, calculate the force of friction between the puck and the ice

9. Example #5 If a box starts with 45J of energy at the top of a ramp but only has 30J of kinetic energy at the bottom of the ramp, how much energy was lost to friction?

10. Example #6 Tony Hawk (78kg) goes up a halfpipe with an initial velocity of 10m/s. If 1000J of energy is lost due to friction, how high up will Tony reach?

11. The Power of the Law of Cons. Of Energy A 70 kg woman and her 35 kg son are standing at rest on an ice rink, as shown above. They push against each other for a time of 0.60 s, causing them to glide apart. The speed of the woman immediately after they separate is 0.55 m/s. After the initial push, the friction that the ice exerts cannot be considered negligible, and the mother comes to rest after moving a distance of 7.0 m across the ice. If their coefficients of friction are the same, how far does the son move after the push? Mom v i = 0.55m/s v f = 0m/s m = 70kg d = 7m Son v i = 1.1m/s v f = 0m/s m = 35kg d = ???