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# 6.3 Elastic and Inelastic Collisions - PowerPoint PPT Presentation

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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#### Presentation Transcript

Date, Section, Pages, etc.

Mr. Richter

• 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

• 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?

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.

• Review HW from 6.2

• Recap Elastic and Inelastic Collisions

• Problem Solving with Elastic and Inelastic Collisions

• Forces in Elastic and Inelastic Collisions

• 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.

• 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.

• 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.

• Both momentum and kinetic energy are conserved in perfectly elastic collisions. Masses separate afterward.

• 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.

• Only momentum is conserved in inelastic collisions. Kinetic energy is lost. Masses stick together afterward.

• 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!

• 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!

• 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.

• p. 230 #1-5