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?