A bouncing rubber ball under a motion sensor is a classic of introductory physics labs. It is often used to measure the acceleration due to gravity, and can also demonstrate conservation of energy. By observing that the ball rises to a lower height upon each bounce, posing the question what is the main source of energy loss? and requiring students to construct their own measured values for velocity from position data, a rich lab experience can be created that results in good student discussions of proper analysis of data, and implementation of models. The payoff is student understanding that seemingly small differences in definitions can lead to very different conclusions.
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