1. Instructor: Dr. Tatiana Erukhimova
Physics 218: Mechanics
Instructor: Dr. Tatiana Erukhimova
Lectures 25, 26

6. Sections 549, 550 105 HELD Sections 551, 552 107 HELD
Second exam Tuesday, October 27
7 pm – 8 pm
Sections 549, HELD
Sections 551, HELD
Section HELD

7. Work Energy Theorem

8. If a force can be written as the gradient (slope) of some scalar function, that force is conservative.
1D case:
U(x) is called the potential energy function for the force
If such a function exists, then the force is conservative

9. does NOT depend on path!
1D case:

10. does NOT depend on path!
If Fx(x) is known, you can find the potential energy function as

11. or

12. Newton’s 2nd Law

13. Work does not depend on the choice of coordinates
Work does not depend on the choice of coordinates! You can calculate work of each force in the most convenient system of coordinates.
Do not forget to work with components!

14. Usually there are several ways to solve the problem.
Indicate the law or the theorem you use!

15. Center of Mass

16. Find the position of the center of mass of the system of the sun and Jupiter. (Since Jupiter is more massive than the rest of the planets put together, this is essentially the position of the center of mass of the solar system.) Does the center of mass lie inside or outside the sun?