Re: Why is percentage rebound of a ball less when dropped from higher height?

Hi Tess,

Not being an expert on the properities of basketballs, I can't answer your 
question directly.  However, I think you're on the right track to answering 
it, yourself.  There are a few things that I would like to point out:

* When you compare percentage rebound distance, you're not getting a 
measure of absolute energy loss.  You're getting a percentage energy 
change.
start with conservation of energy: m*g*h1 + E1 = m*g*h2 + E2
after some algebra: h2/h1 = (E1-E2)/(m*g*h1)

* The reason I point this out is that I don't know if the energy 
transferred after the bounce is a function of the height from which it was 
dropped or if it was function of the velocity when it hits the ground.  If 
it is a linear function of height ( E1 - E2 = A*h1, where A is some number 
irrespective of height ) then you would see a constant percentage of the 
rebound.  However, if E1-E2 were a constant for any height you dropped it 
from, then you would see a percentage rebound that decreased with 
increasing height.  You might want to make a plot of absolute energy change 
(E1-E2) versus height dropped and versus speed just before it hits the 
ground, and whatever else you can think of.  This way, you might be able to 
make some concrete conclusions.

* Unless you have some sophisticated equipment I don't think you will be 
able to tell the difference between energy transferred to heat and energy 
transferred to sound and energy transferred to rotation (the ball may 
spinning and bouncing at the same time)  You can avoid this by either 
asking your question more generally:  Is more of the kinetic energy lost 
when the ball falls from a greater height?

* There are many variables beyond your control that could affect your 
experiment.  Sometimes these might make the ball rebound higher, other 
times they might make the rebound lower.  I would suggest that you perform 
as many reptitions as possible, for example, you might drop the ball from 
each height fifty or a hundred times.  In this way, you can "average out" 
the effects you can't control.

Troy