1. Section 2: Conservation of Energy
Chapter 4: Energy
Section 2: Conservation of Energy

2. Warm Up
A kg marble rolls down a ramp. At a height of 0.5 m, its velocity is 3 m/s.
Find the GPE for the marble.
Find KE for the marble.

3. Transforming Energy
Energy can change types – it can be transformed

4. Can you find the energy transformation?
Electrical energy is converted to….
Electromagnetic energy (visible light energy) which is converted to….
Mechanical energy (sound energy) which is converted to….
Thermal energy (feel the back of TV or screen sometime)
Chemical energy (from gasoline) is converted to…
Mechanical energy (engine starts working and moves the car) which is converted to…
Sound energy, which is converted to….
Heat energy (don’t touch the engine!)

5. Mechanical Energy
Mechanical Energy is the total amount of Kinetic Energy and Potential Energy in a system
A system is a group of objects that work together

6. Mechanical Energy
ME = KE + PE ME = ½ mv2 + mgh

7. Mechanical Energy For a falling object:
GPE decreases because height decreases
KE increases because gravity increases v

8. Mechanical Energy
What is the mechanical energy of a 75 kg man on a diving board 10 m above the ground?
The man jumps. After he has fallen 5 m, he is traveling about 9.9 m/s. Find the mechanical energy of the man.

9. Law of Conservation of Energy
Energy is never created or destroyed,
only transferred or transformed
* The total amount of energy in a closed system never changes

10. Conservation of Energy
Why do we lose mechanical energy?
Friction changes kinetic energy to heat energy, which is lost to the surroundings

11. Losing Kinetic Energy to Friction