00042___b7201019376a8127a035e0350adcc0fc - Sec. 1.6 P...

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Sec. 1.6 PROTOTYPE OF WAVE DYNAMICS 21 application to an experiment initiated by John Hopkinson (1872) who hang a steel wire vertically from a ceiling, attached a stopper at the lower end as shown in Fig. 1.6:1, then dropped a massive weight down the wire from a measured height. When the weight struck the stopper, it stretches the wire suddenly. Hopkinson’s intention was to measure the strength of the wire with this method. Using different weights dropped from different heights, he found that the minimum height from which a weight had to be dropped to break the wire was, within certain limits, almost independent of the magnitude of the weight, and the diameter of the wire. Now, when different solid bodies are dropped from a given height, the velocity reached at any given time is independent of the weight. Thus Hopkinson explains his result on the basis of elastic wave propagation. Equation (8) shows that the stress is equal to pcw. The speed of sound of longitudinal waves in the wire, given by Eq. (5)
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This note was uploaded on 01/04/2012 for the course ENG 501 taught by Professor Thomson during the Fall '05 term at MIT.

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