# Linear Momentum in Collisions

Goal: To investigate the Law of Conservation of Linear Momentum in collisions

Simulation Used: Collision Lab from the PhET at the University of Colorado.

## Preliminary Settings.

• Open the simulation Collision Lab.
• From the menu on the right, select: Show Values
• In the yellow window below, click on “More Data”

## Activity 1: Elastic Collisions: Ball 2 is initially at rest.

On the menu to the right, slide the indicator all the way to the right for a perfectly elastic collision.

For the given masses and initial speeds of the two balls, determine the velocity and momentum after the collision.

#### Run 1.

 Ball Mass (kg) Before the Collision After the Collision v (m/s) P=mv (kg.m/s) v (m/s) P=mv (kg.m/s) Ball 1 0.50 1.20 Ball 2 0.50 0

#### Run 2.

 Ball Mass (kg) Before the Collision After the Collision v (m/s) P=mv (kg.m/s) v (m/s) P=mv (kg.m/s) Ball 1 1.5 0.9 Ball 2 0.50 0

#### Run 3.

 Ball Mass (kg) Before the Collision After the Collision v (m/s) P=mv (kg.m/s) v (m/s) P=mv (kg.m/s) Ball 1 0.50 1.4 Ball 2 1.5 0

Question: Is the momentum conserved for each run?

Question: Is the energy conserved for each run?

## Activity 2: Elastic Collisions: Balls 1 and 2 initially moving in the same direction.

Ball 1 and Ball 2 initially moving in the same directions

#### Run 1.

 Ball Mass (kg) Before the Collision After the Collision v (m/s) P=mv (kg.m/s) v (m/s) P=mv (kg.m/s) Ball 1 0.50 0.80 Ball 2 0.50 0.30

Question: Is the momentum conserved?

Question: Is the energy conserved?

## Activity 3: Elastic Collisions: Balls 1 and 2 initially moving in the opposite direction.

Note that when Ball 2 moves opposite to Ball 1, its velocity and momentum are negative!

#### Run 1.

 Ball Mass (kg) Before the Collision After the Collision v (m/s) P=mv (kg.m/s) v (m/s) P=mv (kg.m/s) Ball 1 0.50 1.20 Ball 2 0.50 -0.30

Question. Is the momentum conserved?

Question: Is the energy conserved?

## Activity 3: Inelastic Collisions

On the menu to the left, slide the indicator all the way to the left to ensure perfectly inelastic collisions

#### Run 1.

 Ball Mass (kg) Before the Collision After the Collision v (m/s) P=mv (kg.m/s) v (m/s) P=mv (kg.m/s) Ball 1 0.50 1.20 Ball 2 0.50 0

Question. Is the momentum conserved?

Question: Is the energy conserved?