In this video, two 0.003 kilogram balls roll toward one another from the opposite ends of a 1.00 meter-long track. The left ball rolls on an inclined track with a constant gentle slope that is about 0.32 meters long and then rolls on a flat track for about 0.12 meters before colliding elastically with the other ball. The right ball rolls on an inclined track with a constant steep slope that is about 0.31 meters long and then rolls on a flat track for about 0.25 meters before colliding elastically with the other ball. The total momentum before an elastic collision can be calculated with the formula (mright ball((xcollision-xright ball pre-collision)/(tcollision-tpre-collision)))+(mleft ball((xcollision-xleft ball pre-collision)/(tcollision-tpre-collision))), with m representing the mass, x representing the ball’s position, and t representing the time at the ball’s corresponding position.
OBSERVATIONS BEFORE THE COLLISION
The following images show positions and times of the ball during the experiment.
mleft ball=0.003 kilograms, xleft ball pre-collision=0.43 meters, mright ball=0.003 kilograms, xright ball pre-collision=0.45 meters, tpre-collision=1.38 seconds |
xcollision=0.44 meters, and tcollision=1.40 seconds |
As observed, the total momentum before the collision is 0 kilograms(meters/seconds).
REFLECTIONS ON BEFORE THE COLLISION
I expected this because the balls were traveling at the same instantaneous velocity just before they collided.
OBSERVATIONS AFTER THE COLLISION
The following images show positions and times of the ball during the experiment.
mleft ball=0.003 kilograms, mright ball=0.003 kilograms, xcollision=0.44 meters, tcollision=1.40 seconds |
xleft ball post-collision=0.43 meters, xright ball post-collision=0.45 meters, and tpost-collision=1.46 seconds |
As observed, the total momentum before the collision is 0 kilograms(meters/seconds).
REFLECTIONS ON AFTER THE COLLISION
I expected this because the balls were traveling at the same instantaneous velocity just after they collided. I also expected the momenta before and after the collision to be equal because in most collisions, the momentum is conserved.
NOTE
The balls never travel at constant velocities due to friction and air resistance, so the closest possible measurable two positions before and after the collision were used to estimate the instantaneous velocity of the balls at these moments.