SAT Subject Physics Practice Question 108: Answer and Explanation

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Question: 108

3. A transverse wave on a long horizontal rope with a wavelength of 8 m travels at 2 m/s. At t = 0, a particular point on the rope has a vertical displacement of +A, where A is the amplitude of the wave. At what time will the vertical displacement of this same point on the rope be –A ?

A. t = s
B. t = s
C. t = s
D. t = 2 s
E. t = 4 s

Correct Answer: D


The time interval from a point moving from its maximum displacement above y = 0 (equilibrium) to its maximum displacement below equilibrium is equal to one-half the period of the wave. In this case

so the desired time is (4 s) = 2 s.

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