# 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 ?

Jan 7, 2018

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
$v = \lambda \cdot f$

Therefore the frequency is
$f = \frac{v}{\lambda}$
$f = \frac{20 \frac{\cancel{m m}}{s}}{0.2 \cancel{m m}} = \frac{20}{0.2} {s}^{-} 1 = 100 H z$

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

I hope this helps,
Steve