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Collisions

Collisions. What is a collision? http :// www.youtube.com/watch?v=W9EqU1_DXUw DON’T TRY THIS AT HOME!!!! . Collisions. A collision occurs when two or more objects interact with each other through forces. Collisions.

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Collisions

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  1. Collisions

  2. What is a collision? http://www.youtube.com/watch?v=W9EqU1_DXUw • DON’T TRY THIS AT HOME!!!! Collisions

  3. A collision occurs when two or more objects interact with each other through forces. Collisions

  4. The objects may actually hit each other during the collision or they may not. (Remember not all forces require objects to be touching to act on them.) • During a collision, momentum is transferred from one object to another. (Remember the money momentum lab?) Collisions

  5. Collisions • According to the law of momentum conservation, the total momentum before the collision is equal to the total momentum after the collision.

  6. Collisions The momentum of the 8 ball after the collision is equal to, less than, or more than the momentum of the cue ball before the collision?

  7. There are two general types of collisions in physics: elastic and inelastic Collisions

  8. In an elastic collision, the objects bounce off each other with no loss in the total kinetic energy and no change in shape. Collisions -The collision of two steel balls is very close to a perfectly elastic collision -Perfectly elastic collisions are not common in the everyday world

  9. In an inelastic collision, objects change shape or stick together, and some kinetic energy is converted to other forms of energy such as heat, deformation, or friction. Collisions

  10. Collisions Inelastic: Objects change shape after the collision

  11. Momentum is conserved in both elastic and inelastic collisions, even when kinetic energy is not conserved. Collisions

  12. Conservation of momentum allows you to determine the speeds and directions of objects before a collision, even if you only know the speeds and velocities after the collision. • Accident investigators often use this approach to determine if anyone was speeding before an automobile accident. Collisions

  13. After the collision Before the collision Collisions Object 1 Object 1 Object 2 Object 2

  14. We can rearrange the formula based on the scenario presented in a collision. Here are some examples: Separate before and separate after. Separate before and together after. m1v1i + m2v2i = (m1+m2)vf Collisions Together before and separate after. (m1+m2)vi = m1v1f + m2v2f

  15. Guided Practice Two 0.165-kg billiard balls roll in the same direction and collide. Initially, the 10 ball has a velocity of 0.5 m/s. The 5 ball has an initial velocity of 0.7 m/s. After the collision, the 5 ball has a velocity of 0.4 m/s. What is the velocity of the 10 ball after the collision?

  16. You try it! Two 0.165-kg billiard balls roll in the same direction and collide. Initially, the 10 ball has a velocity of 0.7 m/s. The 5 ball has an initial velocity of 0.4 m/s. After the collision, the 5 ball has a velocity of 0.2 m/s. What is the velocity of the 10 ball after the collision?

  17. Guided Practice Kevin is rolling along on his 2.0 kg skateboard with a constant speed of 5.0 m/s when he jumps off the back and continues forward with a velocity of 2.2 m/s relative to the ground. This causes the skateboard to go flying forward with a speed of 14.5 m/s relative to the ground. What is Kevin’s mass?

  18. You try it! Kevin is rolling along on his 4.0 kg skateboard with a constant speed of 3.0 m/s when he jumps off the back and continues forward with a velocity of 2.0 m/s relative to the ground. This causes the skateboard to go flying forward with a speed of 15.5 m/s relative to the ground. What is Kevin’s mass?

  19. Guided Practice A 620 kg moose stands in the middle of the railroad tracks, frozen by the lights of an oncoming 10,000-kg locomotive that is traveling at 10 m/s. The engineer sees the moose but is unable to stop the train in time and the moose rides down the track sitting on the cowcatcher. What is the new combined velocity of the locomotive and the moose?

  20. You try it! A 420 kg moose stands in the middle of the railroad tracks, frozen by the lights of an oncoming 12,000-kg locomotive that is traveling at 30 m/s. The engineer sees the moose but is unable to stop the train in time and the moose rides down the track sitting on the cowcatcher. What is the new combined velocity of the locomotive and the moose?

  21. You try it! To test the strength of a retainment wall designed to protect a nuclear reactor, a rocket-propelled F-4 Phantom jet aircraft crashed head on into a concrete barrier at a high speed in Sandia, New Mexico on April 19, 1988. The F-4 Phantom jet aircraft had a mass of 19100 kg, while the retainment wall’s mass was 46900 kg. The wall sat on a cushion of air that allowed it to move during impact. If the wall and the F-4 moved together at 8.41 m/s during the collision, what was the initial speed of the F-4 Phantom?

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