The Physics Factbook
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The purpose of this experiment is to determine the coefficient of restitution for various balls.
The coefficient of restitution is the ratio of speeds of a falling object, from when it hits a given surface to when it leaves the surface. In laymen's terms, the coefficient of restitution is a measure of bounciness. A ball is a round or spherical object that is used most often in sports and games. Balls are made from different materials, but leather, rubber, and synthetics are the most common in modern times.
Balls have been a major part of almost all civilizations history. Some form of ball game is portrayed on early Egyptian monuments. Each spring two large groups of people, each representing one of their gods, acted out a contest that used a round, wooden ball and crooked sticks. The object was to drive the ball through the opposing goal which is the basis for almost all of today's modern ball games. Even among the Romans, who disliked participatory sports, ball play was extremely popular. The Roman baths set aside apartments for ball play, and many gentlemen had ball courts in their private villas. The ancient Roman ball was usually made of leather strips sewn together and filled with various materials, including animals.
The coefficient of restitution is found by the formula
Coefficient of Restitution = speed up / speed down.
In order to find speed we had to use the average height, that we measured, and put it in the formula
v = √(2gh)
Where v = velocity, g = 9.8m/s2, and h = average height measured.
We took the average of the bounced height value (h) and put it in the formula along with the initial height (H) of 92 cm.
Coefficient of Restitution = √(2gh)) / √(2gH) = √(h/H)
The results were then compiled in the table below (xls copy).
|object||H (cm)||h1 (cm)||h2 (cm)||h3 (cm)||h4 (cm)||h5 (cm)||have (cm)||c.o.r.|
|range golf ball||92||67||66||68||68||70||67.8||0.858|
|steel ball bearing||92||32||33||34||32||33||32.8||0.597|
|ball of rubber bands||92||62||63||64||62||64||63.0||0.828|
|hollow, hard plastic ball||92||47||44||43||42||42||43.6||0.688|
Jamin Bennett, Ruwan Meepagala -- 2006
Students Choice pages in The Physics Factbook™ for 2006
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