# Coefficient of Restitution

### Introduction

When playing basketball, the ability of the ball to bounce is a necessary part of the game. If the ball is too bouncy or not bouncy enough then the game will be heavily affected in terms of difficulty of dribbling and shooting. The bounciness of a basketball can be measured with the coefficient of restitution. There are many factors that affect the coefficient of restitution such as: the surface the ball is bounced on, the material the ball is made out of, and the pressure inside of the ball to name a few. I will be measuring the coefficient of restitution for a basketball with different pressures while keeping the other factors constant.

# Data Collection

I first used an electric ball pump with a pressure gauge to measure the pressure of the air inside of the ball. I pumped the basketball up to 10 PSI, 15 PSI, 20 PSI, 25 PSI, and 30 PSI.

I then used logger pro and it's video analysis tools to measure the height of the basketball before and after I dropped it onto tile flooring. I ran five trials at each of the above pressures for a total of 25 trials.

# Data Analysis

My next step was to find the coefficient of restitution for each of my trials. Since I performed 5 trials at each pressure, I calculated the average coefficient of restitution for each pressure. The equation for the coefficient of restitution when the coefficient of restitution is e is e=(height after/height before)^1/2.

Finally, I put the calculations for the average coefficient of restitution and pressure into logger pro to get a graph of the coefficient of restitution vs. pressure. I set a curve fit to the data that tracks the approximate coefficient of restitution for a basketball with the given pressure on tile flooring.

Conclusion:

The higher the coefficient of restitution, the higher the ball will bounce. As the pressure in a basketball is increased, the coefficient of restitution is increased as well. If a basketball is too bouncy then that means that the coefficient of restitution is too high and a solution may be to decrease the pressure in the ball.

It would have been interesting to see the change in the coefficient of restitution for different types of flooring such as wood and concrete.

Works Cited

"UCSB Science Line Sqtest." UCSB Science Line Sqtest. N.p., n.d. Web. 16 Dec. 2014.

"Coefficient of Restitution." In Sports. N.p., n.d. Web. 16 Dec. 2014.