PHYS4A/ Fall 2014; Collisions in Two-Dimensions

Purpose: To create 2-D elastic collisions between two metal balls. Conservation of energy is used to determine the loss from rolling friction.

Two steel balls sitting on top of a glass surface

Setup with the glass surface and a camera above looking down on the glass. 

Paige setting up the balls for collision and making sure they are in view. 

In this experiment, we are making more collisions to practice how to calculate different things using real world examples . In this case, we are creating 2-D collisions between two metal balls and calculating the changes in momentum after collision. The first collision uses an aluminum ball which collides with a steel ball of more mass. The second collision uses two steel balls which and momentum was again calculated. To set up the collision, one ball was set in middle of the surface and the other ball was set with an initial velocity towards the first ball. The camera connected to logger pro was able to record the paths of the ball using the video analysis software. This analysis was used to create postition vs time graphs. The linear fit of each graph was performed with the slope being equal to the velocity of the ball.

Trial 1 with aluminum ball and steel ball

Trial 2 with two steel balls

After obtaining all the velocity values, energy was calculated for all of the runs. 

Energy after first collision 

Energy after second collision

Since these are not perfectly elastic collision, you can see that energy is not conserved. However, momentum is conserved.