and the Physics of Bounce
Obj: Determine COR of several energy balls; graphically analyze a bounce
Materials: various bounce balls, high energy balls, meter stick
I. Coefficient of Restitution COR (vreturn/vimpact)
1. Mass the high energy ball. Place vertically a meter stick on the lab table.
2. From 1 meter, drop the ball, then accurately determine and record the height to which it returned.
3. Repeat four times, each time starting at the return height of the previous trial.
4. For each bounce,
i. Determine the impact velocity and the upward bounce velocity.
ii. Plot a graph of vreturn vs vimpact (x-axis) then determine the COR.
iii. calculate the amount of kinetic energy lost (mgΔh) upon each bounce and the percent.
5. Where is the lost kinetic energy going? Is bouncing elastic or inelastic for this lab?
6. Suggest a formula for COR using the heights of drop and return, then verify it for one of your trials.
7. Estimate the COR for a golf ball, tennis ball, and one other ball using your equation for heights of drop and return.
8. For a perfectly elastic collision what is the COR.
9. On your graph, sketch a line for a perfectly elastic collision and one that is totally inelastic.
10. Most rubber products have a specific heat of 1600 J/kg oC. Assuming the ball absorbs all of the lost kinetic energy as heat, calculate the temperature change for one of your rubber ball trials.