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Applying Dynamics to the Bouncing of Game Balls: Experimental Investigation of the Relationship Between the Duration of a Linear Impulse During an Impact and the Energy Dissipated.

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2012 ASEE Annual Conference & Exposition


San Antonio, Texas

Publication Date

June 10, 2012

Start Date

June 10, 2012

End Date

June 13, 2012



Conference Session

Mechanics Classroom Demonstrations

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Page Count


Page Numbers

25.201.1 - 25.201.12

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Paper Authors


Josué Njock-Libii Indiana University-Purdue University, Fort Wayne

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Josué Njock Libii is Associate Professor of Mechanical Engineering at Indiana University-Purdue University, Fort Wayne, Fort Wayne, Ind., USA. He earned a B.S.E. in civil engineering, an M.S.E. in applied mechanics, and a Ph.D. in applied mechanics (fluid mechanics) from the University of Michigan, Ann Arbor, Mich. He has worked as an engineering consultant for the Food and Agriculture Organization (FAO) of the United Nations and been awarded a UNESCO Fellowship. He has taught mechanics and related subjects at many institutions of higher learning, including the University of Michigan, Eastern Michigan University, Western Wyoming College, Ecole Nationale Supérieure Polytechnique, Yaoundé, Cameroon, and Rochester Institute of Technology (RIT), and Indiana University-Purdue University, Fort Wayne, Fort Wayne, Ind. He has been investigating the strategies that engineering students use to learn applied mechanics and other engineering subjects for many years. He has published dozens of papers in journals and conference proceedings.

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Applying Dynamics to the bouncing of game balls: experimental investigation of the relationshipbetween the duration of a linear impulse during an impact and the energy dissipated.AbstractThis paper discusses experiments done as a class assignment in a Dynamics course in order toinvestigate the relation between the duration of a linear impulse and the energy dissipated duringimpact. After analysis had been presented in lecture on the relation between work and energy andon the connection between linear impulse and linear momentum, a series of distinct but relatedprojects was assigned as hands-on applications of the results of analysis.In project one, it was shown that the height to which a dropped ball rebounded depended uponthe height from which it was dropped. The ratio consisting of the rebound height divided by thedrop height was found to decrease with increasing drop heights. This pattern held true withbasketballs, tennis balls, ping pong balls, volleyballs, and racket balls. In project two, therebound height of a basketball was investigated as a function of the inflation pressure of thebasketball. It was determined that the rebound height increased with increases in the inflationpressures. In project three, experiments that would allow for the collection of data to help explainthe results of projects one and two were designed and carried out.First, the relationship between the mechanical energy dissipated by a ball bouncing off a rigidsurface and the duration of the impact was investigated experimentally. Three different kinds ofballs were used: basketballs, tennis balls, and ping pong balls. Data were collected using digitalcameras and processed using software freely available on the web.For each of the tested balls, experimental data showed that when the duration of impactsincreased, so did the amount of energy that was dissipated. Similarly, when the duration ofimpact decreased, so did the amount of energy that was dissipated. Consequently, for each testedball, the longer the duration of the impulse, the more energy was dissipated.The engineering curricula at our university are arranged in such a way that students usually takeStrength of Materials and Dynamics during the same semester. Such students reported that thisproject allowed them to start to see that relationships did exist among the energy dissipated bybouncing balls during impact, the deformation undergone by the balls, and the properties of thematerials of which the balls are made. The fact that students began to uncover such connectionson their own was very satisfying.

Njock-Libii, J. (2012, June), Applying Dynamics to the Bouncing of Game Balls: Experimental Investigation of the Relationship Between the Duration of a Linear Impulse During an Impact and the Energy Dissipated. Paper presented at 2012 ASEE Annual Conference & Exposition, San Antonio, Texas.

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