Please wait for the animation to completely load.

The animation shows an elastic collision between two masses (position is given in centimeters and time is given in seconds). Restart.

1. Set the initial velocity of the blue ball to zero. For the three conditions of the relative masses of the blue and red balls shown in the table, PREDICT what value (or values) of the initial velocity of the red ball will result in...

• both balls moving to the right after the collision.
• the red ball stopping after hitting the blue ball.
• the red ball moving to the left and the blue ball moving to the right after the collision.

AFTER you have made your predictions, test them using the animation. Were you correct? If not, explain.

2. Now set the initial velocity of the blue mass to -20 cm/s, the initial velocity of the red mass to 5 cm/s, and the masses equal. PREDICT the direction each ball will be traveling after impact. AFTER you have made your prediction, try it. Were you correct? If not, explain.
3. Set the initial velocity of the blue mass to -10 cm/s and the red mass to half the mass of the blue ball. PREDICT the velocity the red mass must have in order to completely stop the blue mass when they collide. Now try it. Were you correct? If not, explain.
4. Set the initial velocity of the blue mass to -10 cm/s and the red mass to twice the mass of the blue ball. PREDICT the velocity the red mass must have in order to completely stop the blue mass when they collide. Now try it. Were you correct? If not, explain.

Exploration authored by Melissa Dancy.