1 / 33

Collisions: Momentum and Impulse

Collisions: Momentum and Impulse. SC.CE.05.01. The product of the mass of an object and its velocity Momentum = “ p ” p= m v If mass is constant, then a change of momentum equals mass times change in velocity: Δ p= m Δ v A vector quantity Vector means…. Momentum:. Impulse:.

Collisions: Momentum and Impulse

An Image/Link below is provided (as is) to download presentation Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

1. Collisions: Momentum and Impulse SC.CE.05.01

2. The product of the mass of an object and its velocity Momentum = “p” p=mv If mass is constant, then a change of momentum equals mass times change in velocity: Δp=mΔv A vector quantity Vector means… Momentum:

3. Impulse: • The average force multiplied by its time interval of action • Impulse = FΔt • A vector quantity • Vector means…

4. Simply stated: • Impulse = change in momentum =Δp

5. Impulse/momentum principle: • The impulse acting on an object produces a change in momentum of the object that is equal both in magnitude and direction to the impulse

6. For example: m=7kg v=2m/s p=14kg ×m/s m=0.07kg v=200m/s p=14 kg × m/s

7. Conservation of Momentum: • When the net external force acting on a system is zero, the total momentum of the system is conserved • In other words: the momentum before a collision will equal the momentum after a collision • When internal forces are equal (but opposite), momentum is conserved

8. Example: • A 100 kg fullback moving straight downfield with a velocity of 5 m/s collides head on with a 75 kg defensive back moving in the opposite direction with a velocity of -4m/s. The defensive back hangs on to the fullback, and the two players move together after the collision. • a. What is the initial momentum of each player? • b. What is the total momentum of the system? • c. What is the velocity of the two players immediately after the collision?

9. Fullback: m = 100 kg v = 5 m/s p = ? p = mv p = Defensive back: m = 75 kg v = -4 m/s p = ? p = mv p = Example (cont’d) a: What is the initial momentum of each player?

10. b. What is the total momentum of the system? • p total = p fullback + p defensive back • p total = 500 kg x m/s + -300 kg x m/s • p total = 200 kg x m/s

11. v=? m= 100 kg + 75 kg =175 kg p=mv So: v=p/m v= 200 kg x m/s 175 kg c. What is the velocity of the two players immediately after the collision?

12. Types of Collisions: Perfectly Inelastic to Perfectly Elastic Extend your knowledge of momentum and energy conservation!

13. Perfectly Inelastic Collisions • A collision in which the objects stick together after colliding • No bounce • If p is known before collision for both objects, we simply add them together to get final p • A lot of the original kinetic energy is transformed • Example: railroad car coupling, two balls of clay, a football tackle

14. Partially Inelastic • Some kinetic energy is transformed

15. Elastic • No kinetic energy is transformed • Atoms collide without “spending” energy

16. When pool balls collide: • Most collisions are elastic: both momentum and kinetic energy are conserved • Momentum is transferred from the cue ball to the target ball • We can determine the velocity of both balls after collision • It gets tricky when multiple pool balls are involved, but I know you can do it!

17. Collisions at an Angle Oh geez, here we go…

18. An Inelastic Two-Dimensional Collision: • Remember that momentum is a vector quantity? • Now our football players from Monday are running perpendicular to one another 583 kg x m/s p2=300kg x m/s 31° p1=500kg x m/s

19. Elastic Two-Dimensional Collisions • Initial kinetic energy = 1/2mv2 must also equal the sum of the kinetic energies

More Related