1. College and Engineering Physics Elastic and Inelastic Collisions 1 TOC Conservation Collisions

2. College and Engineering Physics Elastic and Inelastic Collisions 2 TOC Conservation of Linear Momentum The change in momentum of a system is equal to the impulse put on the system.

3. College and Engineering Physics Elastic and Inelastic Collisions 3 TOC Conservation of Linear Momentum For example: Jeff Bagwell hits a baseball… Initially

4. College and Engineering Physics Elastic and Inelastic Collisions 4 TOC Conservation of Linear Momentum For example: Jeff Bagwell hits a baseball… During hit

5. College and Engineering Physics Elastic and Inelastic Collisions 5 TOC Conservation of Linear Momentum For example: Jeff Bagwell hits a baseball… Finally

6. College and Engineering Physics Elastic and Inelastic Collisions 6 TOC Two types of collisions Elastic: The objects do not stick together or change shape. Momentum and kinetic energy are conserved. Inelastic: The objects do stick together and/or change shape. Only momentum is conserved!

7. College and Engineering Physics Elastic and Inelastic Collisions 7 TOC Example of an elastic collision The cue ball hits two billiard balls initially at rest on a billiard table. Assume that the cue ball stops after hitting the other balls. What is the final velocity of the red and blue ball? x y θ

8. College and Engineering Physics Elastic and Inelastic Collisions 8 TOC x y θ

9. College and Engineering Physics Elastic and Inelastic Collisions 9 TOC x y θ

10. College and Engineering Physics Elastic and Inelastic Collisions 10 TOC x y θ We have three equations and four unknowns. We cannot solve this problem without more information. You will usually be given the speed or angle of one of the balls.

11. College and Engineering Physics Elastic and Inelastic Collisions 11 TOC Example of an inelastic collision A pieces of putty is thrown against a box sitting at rest on a frictionless table. If the putty is twice the mass of the box, what is the speed of the box/putty combination compared to the original speed of the putty?

12. College and Engineering Physics Elastic and Inelastic Collisions 12 TOC Impulse and Momentum Momentum Impulse x-component The total impulse acting on a systems is ALWAYS equal to the change in its momentum

13. College and Engineering Physics Elastic and Inelastic Collisions 13 TOC Impulse and Momentum Elastic Collisions Inelastic Collisions Object 1Object 2 p 0x 2 kg m/s1 kg m/s p fx -3 kg m/s6 kg m/s p 0y 0 kg m/s p fy 2 kg m/s-2 kg m/s K0K0 12 J6 J KfKf 8 J10 J Object 1Object 2 p 0x 1 kg m/s p fx -3 kg m/s5 kg m/s p 0y 2 kg m/s0 kg m/s p fy 3 kg m/s-1 kg m/s During collisions momentum is always conserved and kinetic energy is sometimes conserved

14. College and Engineering Physics Elastic and Inelastic Collisions 14 TOC This is the last slide. Click the back button on your browser to return to the Ebook.