Teaching Physics with the Physics Suite Edward F. Redish Problems Sorted by Type | Problems Sorted by Subject | Problems Sorted by Chapter in UP

Varying a pulse*

A long, taut string is attached to a distant wall (see figure). A demonstrator moves her hand and creates a very small amplitude pulse that reaches the wall in a time t0. A small red dot is painted on the string halfway between the demonstrator's hand and the wall. For each item, state which of the actions 1-10 listed below taken by itself will produce the desired result. For each question, more than one answer may be correct, If so, give them all.

How, if at all, can the demonstrator repeat the original experiment to produce:

1. A pulse that takes a longer time to reach the wall.
2. A pulse that is wider than the original pulse.
3. A pulse that makes the red dot travel a further distance than in the original experiment.

 Move her hand more quickly (but still only up and down once and still by the same amount) Move her hand more slowly (but still only up and down once and still by the same amount). Move her hand a larger distance but up and down in the same amount of time. Move her hand a smaller distance but up and down in the same amount of time. Use a heavier string of the same length under the same tension. Use a lighter string of the same length under the same tension. Use a string of the same density, but decrease the tension. Use a string of the same density, but increase the tension. Put more force into the wave. Put less force into the wave.

* From the Wave Test by M. Wittmann