John Wiley & Sons, 2007
John Wiley & Sons, 2007 |
A central experiment in the modern mechanics semester is a measurement of Young's modulus, from which we extract by a macro-micro analysis the effective stiffness of the interatomic bond, modeled as a spring in the ball-and-spring model of solids. Here we show pictures of the apparatus that students use in the lab. A wire nearly 2 meters long goes from the bottom of the upright frame over two pullies and down to a slider that passes through a slot marked in millimeters. Accuracy is limited more by the difficulty to eliminate all kinks in the long wire than by how well the stretch can be measured, so for directness and simplicity we don't have a Vernier scale (whose use would have to be explained). The goal is not to get a high-precision measurement of Young's modulus but rather to give students a feeling for the nature of the phenomenon and the size of the effects. The base comes off so that the base and upright frame stack for compact storage.
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