1. Physics 218: Mechanics Instructor: Dr. Tatiana Erukhimova Lecture 24

2. Ex.6 This is a one dimensional problem. A particle of mass m is attracted to the origin with a force of magnitude If a particle starts at x=A, moving to the right with velocity V 0, where will it turn around? Could there be no solution? x=0 x=A x V0V0

4. Quiz A particle can only move along the x axis. Forces act on it so that its potential energy function is where k 1 and k 2 are positive. The particle is started at x=a with zero velocity. a)Where is the velocity a maximum? What is its magnitude? b) Where else will the velocity be zero? c)What is the force on the particle as a function of x?

8. Second exam Tuesday, October 21 105 Heldenfels Section 801 and half of 802 start at 7 pm Section 803 and half of 802 start at 8:15 pm

9. Work Energy Theorem

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

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

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

13. or

14. Kinematics:

15. If is given, you can find and

16. Newton’s 2nd Law

17. 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!

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

19. We will have a regular class on Wednesday!

20. Help Session: When: tonight at 7:00 pm Where: Room 207 James J. Cain Engineering/Physics Lab Building Spence St.

21. Have a great day! Hw: Be prepared for the test Good luck!