Question

Ripples are produced on water surface in a bucket. the separation between consecutive crests is mm and the ripples produced on surface at a speed of 2 cm per second. How many crests hit the wall of the container per second ?

Answer 1

100 crests hit the wall of the container per second.

Explanation:

To make our length units consistent, I will convert the speed to 20 mm/s. The formula that relates speed, v; wavelength, `lambda`; and frequency, f; is
`v = lambda*f`

Therefore the frequency is
`f = v/lambda`
`f = (20 cancel(mm)/s) / (0.2 cancel(mm)) = 20/0.2 s^-1 = 100 Hz`

Therefore, 100 crests hit the wall of the container per second.

I hope this helps,
Steve