Collision Course:

Elastic and Inelastic Collisions

Corina Bot, PhD (NJIT, C2PRISM)Keri Salvador (NJIT, C2PRISM)Caroline Savio (ESHS, NPS)

Career DayMay 11th, 2010

Outline of Presentation

About Collision Course Applet

Lesson Plan in Conjunction with Applet

Conclusion and Questions

Concepts Behind Collision Course Applet

Used to distinguish elastic and inelastic collisions

Conservation of momentum

ffii

ffii

vvvv

vmvmvmvm

2121

22112211

momentum before collision = momentum after collision

results before = results after

Elastic collision Conservation of momentum

m1v1i m2v2i m1 m2 v fmomentum before collision = momentum after collision

Inelastic collision Conservation of momentum

results before = results after

Introduction to Collision Course Applet

Designed by C2PRISM Fellow Corina Bot, PhD. Dr. Bot interviewed six Advanced Placement Physics

students at once via focus-group .

Students really liked the idea of acquiring a physics concept shaped as a game.

Features of Collision Course Applet

Multiple choice question game Takes place in neutral settingPlayer chooses which car to driveContains sound effectsVisible damage in the cars after collisionsCartoon policeman assigns ticket at collision

scene Player must distinguish whether collision was elastic or

inelastic A correct answer -> policeman gives you points and your

ticket is void An incorrect answer -> policeman gives you a ticket and

you lose points

Specifics on Applet Creation

Java applet developed by software engineer students at NJIT

Flash software/plug-in required

PC and Mac OS Compatible

Outline of Presentation

Lesson Plan in Conjunction with Applet

Lesson Plan in Conjunction with Applet

Engagement and Assessment

Ideally, students work independently on applet using computers in lab classroom. If there are not enough computers in classroom, work

in pairs. Or perform applet in computer lab instead of physics

lab.

Formative Check The applet consists of multiple choice questions that

evaluate the student’s understanding of types of collisions.

Lesson Plan in Conjunction with Applet

Some practice problems Mario and Luigi on Bumper Cars

The physics classroom http://www.physicsclassroom.com/Class/momentum/u

4l2d.cfm

Elastic collision Input: m1 = 300 kg m2 = 400 kg v1i = 20 km/h v2i = 0 km/h

Calculate: v1f =? v2f = ?

Momentum is conserved!

Solution

h

km

h

km

h

km

h

kmvv

h

km

h

kmv

vkgh

kmkg

h

kmkgvkgvkg

h

kmkg

h

kmvkgvkg

h

kmkg

h

kmvv

vvh

km

vkgvkgh

kmkg

vkgvkgh

kmkg

vvvv

vmvmvmvm

ff

f

f

ff

ff

ff

ff

ff

ff

ffii

ffii

14.172085.220

85.2700

2000

7002000

80004003006000

204003006000

)4(20

020

)3(4003006000

400300020300

)2(

)1(

12

1

1

11

11

12

21

21

21

2121

22112211

Substitute values given in problem into equation (1):

Substitute values given in problem into equation (2):

Substitute equation (4) in equation (3):

Inputs: m1 = 300 kg m2 = 400 kg v1i = 20 km/h v2i = 0 km/h

Calculate: v1f=? v2f = ?

Inelastic collision

Input: m1 = 300 kg m2 = 400 kg v1i = 20 km/h v2i = 0 km/h Calculate: vf = ?Calculate: momentum before & after collision

Momentum is conserved!

Solution

h

km

h

kmv

vkgh

kmkg

vkgkgh

kmkg

vmmvmvm

f

f

f

fii

57.8700

6000

7006000

400300020300

212211

h

kmkg

h

kmkg

h

kmkgkg

h

kmkg

vmmvmvm fii

59996000

57.8400300020300

212211

momentum before collision = momentum after collision

Inputs: m1 = 300 kg m2 = 400 kg v1i = 20 km/h v2i = 0 km/h

Calculate: vf=?

Conclusions

Many senses engaged in learning process Group discussion with class Group instruction with visual demonstration Independent work on applet and on practice problems Paired work (optional)

Students will qualitatively and quantitatively distinguish elastic from inelastic collisions.

Questions?

Thank You!