Two children shake the ends of a skipping rope…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two children shake the ends of a skipping rope. A pulse high runs to the right, and a pulse high runs to the left. Both are above the rope's rest line.
- How high is the rope at the moment the two pulses overlap exactly?
- They try again, but now the second pulse is below the rest line. Where is the rope at the moment of overlap?
- What do the pulses look like after they have passed each other?
Need a reminder? The key ideaShow
Superposition: where waves meet, their displacements add, . Two waves of amplitudes and with a phase difference give ; for equal amplitudes, . A path difference is a phase difference . Intensity .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
(a) above the rest line.
(b) above the rest line.
(c) Each pulse goes on with its own height and shape: up moving right, and up (or down) moving left. Waves pass through each other unchanged.
Answer: , then , and both pulses come out as they went in.
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