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6.3 Elastic and Inelastic Collisions

6.3 Elastic and Inelastic Collisions. Date, Section, Pages, etc. Mr. Richter. Agenda. Today: Warm Up Review HW from 7.1 Practice Problems for 7.2 Intro to Collisions (7.3) Tomorrow Conservation of Momentum Lab Thursday: Review HW from 7.2 Finish Collisions (7.3) Friday:

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6.3 Elastic and Inelastic Collisions

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  1. 6.3 Elastic and Inelastic Collisions Date, Section, Pages, etc. Mr. Richter

  2. Agenda • Today: • Warm Up • Review HW from 7.1 • Practice Problems for 7.2 • Intro to Collisions (7.3) • Tomorrow • Conservation of Momentum Lab • Thursday: • Review HW from 7.2 • Finish Collisions (7.3) • Friday: • Problem Solving Practice • Monday: • Concepts Review • Tuesday • Chapter 6 Test

  3. Warm-Up: • Assume two cars have the same mass and speed going into a collision. • Scenario A: Two cars collide with each other but bounce off. Neither of them sustain noticeable damage. • Scenario B: Two cars collide with each other and crumple, sticking together after the crash. • In which scenario do you think energy is conserved? • In which scenario do you think the driver feels more force?

  4. Conservation of Momentum Practice Problems

  5. Practice Problems • Recoil: A boy on a skateboard initially at rest tosses an 8.0 kg jug of water in the forward direction at a speed of 3.0 m/s. If the boy and the skateboard move backward at 0.60 m/s, find the mass of the boy. • Collision: p. 234 #39 • As long as everything is in grams (g) and centimeters per second (cm/s), THERE IS NO NEED TO CONVERT.

  6. Agenda • Review HW from 6.2 • Recap Elastic and Inelastic Collisions • Problem Solving with Elastic and Inelastic Collisions • Forces in Elastic and Inelastic Collisions

  7. Objectives • Identify different types of collisions. • Calculate change in kinetic energy (or lack thereof) in different types of collisions. • Find the final velocity of objects in different types of collisions. • Understand the relationship between the type of collision and the force experienced by the object.

  8. Elastic Collisions

  9. Collisions • Collisions can be categorized into two types: • elastic • inelastic • Elastic collisions are when objects bounce off of each other. • (Elastics are like rubber bands, and rubber bounces) • Scenario A. • Inelastic collisions are when objects stick together after the crash. • Scenario B.

  10. Elastic Collisions • In perfectly elastic collisions objects: • Bounce off each other • No loss of energy due to speed (kinetic energy) • No change of shape. • In real life, there are almost no perfectly elastic collisions. • Almost always, some energy is lost to sound or heat in a collision.

  11. Elastic Collisions: Awesome Examples

  12. Elastic Collisions: Problem Solving • Both momentum and kinetic energy are conserved in perfectly elastic collisions. Masses separate afterward.

  13. Practice Problem

  14. Inelastic Collisions

  15. Inelastic Collisions • In inelastic collisions objects: • Stay stuck together • Kineticenergy is lost to: • Primarily internal energy • Heat • Sound • Objects are deformed (shape is changed. • In real life, most collisions are a combination of elastic and inelastic collisions. Objects will deform a little, and separate a little.

  16. Inelastic Collisions: Awesome Example

  17. Inelastic Collisions: Problem Solving • Only momentum is conserved in inelastic collisions. Kinetic energy is lost. Masses stick together afterward.

  18. Practice Problem

  19. Forces in Collisions

  20. Forces in Collisions • Assume two objects that have the same mass and the same speed collide with each other. • In which type of collision do they experience a greater change in momentum? • inelastic (both vehicles stop) • elastic (both vehicles stop and reverse direction) • Elastic collisions have greater changes in speed, thus the objects experience more force!

  21. Forces in Collisions: Examples • Think of a batter in baseball. Does the baseball experience more force when the batter: • bunts (inelastic) • hits a home run (elastic) • Your car is designed to crumple (inelastic), so that you experience less force. • Greater changes in momentum mean more force. Elastic collisions are more forceful!

  22. Wrap-Up: Did we meet our objectives? • Identify different types of collisions. • Calculate change in kinetic energy (or lack thereof) in different types of collisions. • Find the final velocity of objects in different types of collisions. • Understand the relationship between the type of collision and the force experienced by the object.

  23. Homework • p. 230 #1-5

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