Washington College
Physics 100

Home experiment #9: Energy loss

Take a tennis ball and drop it from a height of 1 m. (All initial energy is potential, PE  = m*g*H). Measure how high it bounces up. Repeat the experiment several times and find the average height h of the ball after the first bounce. From these results answer the following questions:

(i) What are the velocities of the ball immediately before and after the bounce? Note: Before the bounce all the initial PE converts into kinetic energy, KE  = (m*v^ 2)/2. Therefore PE (at top) = KE (at bottom). After the bounce all remaining KE converts into PE at the highest point.

(ii) What fraction of the total energy is lost during a bounce?

(iii) How many bounces (minimum number) are needed to reduce the total initial energy by a factor larger than 10 ?

(v) Based on your trial to trial height variation, what is the uncertainty in your results (i) - (iv)?