- #1

jfnn

## Homework Statement

[/B]

Hi,

I have a quick question regarding elastic and inelastic collisions. I preformed an experiment in my house with two large, heavy marbles. I rolled one horizontally towards a stationary one, recorded a video of the collision. I uploaded the video to Tracker software, obtained motion graphs for each, and calculated the horizontal and vertical velocities. I then used pythagoreans theorem to find the scatter angle. I got 28 got marble one and 31 for marble two.

My question is, after plugging these values with the velocity obtained into the conservation of momentum equation, I see that momentum is conserved, which is a good thing.

However, how can I tell if the collision is elastic or not? I tried looking at the relationship between the kinetic energy and found that it was NOT constant. If it was not constant, would that be enough to say the collision was inelastic?

I also add those two angles, which do not add up to 90 degrees. For an elastic collision, the angles should add up to 90 degrees for two identical masses; however, it does not, it is not even close! Is this further evidence to show that the collision is inelastic?

Does it make sense for the collision to be elastic AT ALL? Like I did this experiment on the hardwood floor in my house, clearly the KE could not be conserved because energy left the system through the friction force and dissipated as heat. Therefore, energy was lost and not constant. Would it be possible to have an elastic collision at all in this situation?

Furthermore: Could there be enough experimental error that my values just deviate so much that the collision should be elastic instead of inelastic? Is my logic wrong?

Thank you so much for your help,

J

## Homework Equations

[/B]

p=mv

KEi=KEf

## The Attempt at a Solution

Mentioned above.[/B]