Passage III

Suppose a ball is dropped from a height H above a horizontal surface. The ball falls straight down until it collides with the surface; then it bounces straight up, attaining a maximum height y before it begins to fall again. The coefficient of restitution, C, for the collision equals .

Therefore:

y=CH

Physics students went to a high-altitude laboratory conduct studies of C for various balls bouncing off different horizontal surfaces. The air temperature and air pressure were constant in the laboratory throughout the studies.

Study 1

The students dropped a racquetball from various H onto a particular horizontal surface, and after each drop they measured y. Then they graphed y versus H(see Figure 1); C equaled the slope of the graph.

Study 2

The students repeated the procedure in Study 1 and determined C for various balls dropped onto both a bare concrete surface and a concrete surface covered with a thin layer of foam. Both surfaces were horizontal. The results are given in Table 1.