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

Sections 549, 550 105 HELD Sections 551, 552 107 HELD Second exam Tuesday, October 27 7 pm – 8 pm Sections 549, 550 105 HELD Sections 551, 552 107 HELD Section 570 109 HELD

Work Energy Theorem

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

does NOT depend on path! 1D case:

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

or

Newton’s 2nd Law

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!

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

Center of Mass

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?