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.

15. Suppose that in Study 2 the steel ball had been dropped onto the bare concrete surface and the foam-covered concrete surface from a height of 2.00 m. Approximately how much lower or higher would the steel ball have bounced after its collision with the bare concrete surface than after its collision with the foam-covered concrete surface?

Answer and Explanation

Your Answer is

Correct Answer is C

Explanation

According to the formula y=CH given in the experiment description, it can be seen that when the initial height H is 1 m, the height of the bounce on the bare concrete surface is 0.65-0.42=0.23 m higher than that on the foam-covered concrete surface, So when the initial height is 2m, the height difference is 0.23×2=0.46 m, close to 0.5 m