Ping Pong Physics

Investigation of The Best Ping-Pong Racquet Material Sarah Don

under the direction of Dr. Malachite Green institute of Ping-Pong Ball Engineering

Research Science Institute June 26, 2008

Abstract This report is an investigation of energy conservation between a ping-pong ball and different materials. Using Ep = mgh, the variation of the bounciness of a pingpong ball on different surfaces could be explained. From the data obtained from the experiment, a conclusion was reached refarding which of the materials tested was the best to manufacture a ping-pong raquet out of.

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Introduction

This report is an investigation of four different surface materials found in Simmons Dorm in order to identify the best material for an improved ping-pong racquet. The four materials are carpet, concrete, wood and linoleum. The ping-pong ball’s responsivness for each surface was observed. The hypothesis tested was that the ping-pong ball bounced a higher number of times when dropped on concrete than on any of the other three surfaces. The controlled variables were the height from which the ping-pong ball was dropped, the ping-pong ball-dropping person, the person who was quiding the ball-dropper, and the same ping-pong ball was used each time. The manipulated variable was the material on which the ping-pong ball was dropped onto each time, and the dependent variable was the number of bounces that the ping-pong ball made with each of the three trials on each type of material.

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Method

Three 30 cm rulers were taped to a vertical wall next to an area of carpet. A ping-pong ball was dropped from 90 cm three times, but for each of the three trails, a person observed the height of the ping-pong ball from eye level and guided the ball-dropper to make sure the drop-height was as close to 90 cm as possible. Then the three rulers were set up again on a vertical wall next to an area of concrete and three trials were carried out. The same procedure was carried out for wood and linoleum until all the trials were completed and recorded.

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Results

All the mean number of bounces for each of the different materials was rounded up to the nearest whole number because once the ping-pong ball has started a fraction of a bounce, it 2

Carpet Concrete Wood Linoleum

Trial 1 Trial 2 Trial 3 3 3 3 13 14 14 19 21 20 15 15 16

Mean 3 14 ± 1 20 ± 1 16 ± 1

Table 1: Results and Statistics

Figure 1: Graph of number of ping-pong ball bounces and their uncertainty

has to complete it. Thus, because counting the number of bounces is discrete, the uncertainty was rounded up to 1. 1 From the graphical representation in the graph above, it can be seen that the wood is the best materical for bouncing a ping-pong ball, and carpet is the worst.1

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Discussion

The results show that wood allowed the ping-pong ball to bounce a higher number of times than other surfaces. The results also show that carpet was the worst material for bouncing a ping-pong ball. There are several factors that may have impacted upon the accuracy of the results obtained. The concrete surface used was rough, uneven and covered in a layer of dust that acted like the carpet, absorbing some of the energy from the ping-pong ball. 3

Ep = mgh Ep = 0.0023 · 9.8 · 0.9 Ep = 0.02J Figure 2: Potential energy of ping-pong ball This increasing loss of energy with each bounce caused the ping-pong ball to bounce a fewer number of times on concrete than on wood or linoleum. The reason that some materials allow the ping-pong ball to bounce higher (therefore, more bounces) is because of Newton’s second law regarding the conservation of energy. Before the ping-pong ball is released, it contains a certain amount of potential energy. 2 [1] As the ping-pong ball lands on the material’s surface, it transfers some of its energy to the material in sound, heat and kinetic energy (in the case of carpet). Some materials, such as carpet, can compress more than wood. The carpet therefore takes more energy from the ping-pong ball than wood does. This leaves the ping-pong ball with less energy to bouce off the surface again, causing it to reach a lower height and subsequently bounce a lower number of times. After carpet, linoleum was the next more springy material, then concrete (because of the dust layer) and the hardest material was wood. As the ping-pong ball lands on the wood, little energy is absorbed by the wood, leaving more energy for the ping-pong ball to continue to bounce.

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Conclusion

The data did not show the results that were initially expected. Therefore the hypothesis was rejected and a new conclusion was reached - out of the materials that were tested, wood is the best material to make a ping-pong racquet out of.

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Acknowledgments

Zhongyuan Zhang, Mary Davies, *Double Happiness* (ping-pong ball manufacturer), Simmons Hall, Research Science Institute, Massachusetts Institute of Technology.

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References [1] Letts, Greg.: The Basic Physics and Mathematics of Table Tennis / Ping-Pong, About.com, 2007.

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