2. Potential Energy Chapter 8 Lecture #1 BY: Dr. Aziz Shawasbkeh Physics Department

3. Outline Potential Energy Conservative forces Determining of potential energy Conservation of Mechanical Energy Potential Energy Curves Work done by non-conservative forces Conservation of total energy Mass and Energy

4. Potential Energy: The Energy associated with the configuration of a system of objects that exert forces on each other Example: Gravitational Potential Energy. Elastic Potential Energy in a spring. Work and Potential Energy: Throwing Pumpkin up: UiUi UfUf mgd

5. Dropping Pumpkin Down: UfUf UiUi mgd

6. Elastic Potential Energy:

7. Conservative forces a b 1 2 A force F acts on an object The object moves along two different paths If W ab1 = W ab2, Then F is conservative

8. The net work done by a conservative force along any closed path is zero W ab1 = W ab2 W ab2 = -W ba2 W ab1 -W ab2 = 0 W ab1 + W ba2 = 0 Closed Path: Conservative force: a b 1 2

9. Examples Gravitational Force: W g = mgh h Elastic force:

10. Determining Potential Energy: Example: Gravitational Potential Energy

11. Take reference point at y i = 0, U i =0, Then Elastic Potential Energy

12. Conservation Of Mechanical Energy If forces acting on the body are conservative

13. Example: Free falling body h

14. Example: At point x= 0 At point x= A