1. Potential Energy Physics 11

2. Potential Energy Potential Energy is energy due to position or stored energy. Stored chemically in fuel, the nucleus of atom, and in foods. Or stored because of the work done on it: Stretching a rubber band.

3. Examples of Potential Energy: Stretching a rubber band.. -Stores energy Water at the top of a waterfall.. -Stores energy Yo–Yo in held in your hand.. -Stores energy because of position Drawing a Bow… -Stores energy because of position

4. When the position of an object is altered, it creates potential energy. If book is picked up from the floor and put on a shelf, it’s position has changed as well as it’s potential energy. There is no absolute zero position or condition. Physicists assign a reference position, therefore only changes in potential energy can be measured. About Reference points…..

5. Gravitational Potential Energy This is one type of potential energy. Potential energy that is dependent on height is called gravitational potential energy. A waterfall, a suspension bridge, and a falling snowflake all have gravitational potential energy.

6. Gravitational Potential Energy: Symbol: E g Product of mass, acceleration due to gravity and change in height mass (kg) height (m) Units = kg(m/s) 2 or N·m or J E g = mg Δh

7. Gravitational Potential Energy “The bigger they are the harder they fall.” It is not just a saying. It’s true. Objects with more mass have greater potential energy.

8. The path doesn't matter, just the change in height:

9. Just like before with E k and work.. E g and work are also closely related. W = ΔE g or W = E g2 – E g1

10. Example #1: A crane lifts a steel beam with a mass of 1,500 kg. Calculate how much work is done against gravity if the beam is lifted 50 meters in the air?

11. W = ΔE g W = mgΔh = (1500)(9.81)(50-0) = 740 000 J

12. Try it : Page 250 #27-29 Page 254 # 30-34 Physics 20 Page 124-125 1-5