Question

Two boats are located 20 m apart. The wavelength of the water waves is 2.5 m. One of the boaters counts 15 waves passing him by in a timer of 10 seconds. How much time does it take for a particular wave to travel between boats?

Answer 1

By definition, the frequency of waves is

$$\nu=15/10 = 1.5 Hz$$

If the wavelength of the wave is $\lambda = 2.5 m$, then the speed of wave is:

$$v =\nu\lambda= 2.5\cdot1.5 = 3.75 m/s$$

Then covering the distance $l = 20m$ between the boards will take:

$$t = l/v = 20 /3.75 \approx5.33 s$$

Answer. t = 5.33 s.