COR
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
Methods
and Analysis
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.