An example problem from my openstax physics textbook:

A student takes a 30.00-m-long string and attaches one end to the wall in the physics lab. The student then holds the free end of the rope, keeping the tension constant in the rope. The student then begins to send waves down the string by moving the end of the string up and down with a frequency of 2.00 Hz. The maximum displacement of the end of the string is 20.00 cm. The first wave hits the lab wall 6.00 s after it was created.

  • (a) What is the speed of the wave?
  1. For part(a), my books says the formula is $v=d/t$ and uses $30\,\mathrm{m}$ as $d .$ My question is that for a wave doesn't $d$ stand for wavelength? Wouldn't that mean that 30 meters isn't lamda?

  2. The above question says that maximum displacement is $20\,\mathrm{cm} .$ What quantity does displacement at the end of the string represent? Is $20\,\mathrm{cm}$ the wavelength?


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The situation described in the picture is something like this.

The distance $d$ is the distance from your hand to the wall, so it is not necessarily the same as the wavelength, though it could be the same. The amplitude $A$ is the vertical displacement.


d is not wavelength.velocity by defination displacement done in unit time then by defination we could directly calculate

V=d/t ( and for time T(timeperiod of wave) wave is λ(wavelength)

V=λ/T or V=λυ(υ is frequency and υ=1/T)) so there should not be any confusion between v=d/t or v=λ/T and 20cm is amplitude as it is maximum displacement of particle from mean(here we knew by particle at end that boy flicks assuming no change in amplitude )


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