Chapter SH, Problem 13.22EP

To determine

To find the time intervals when buoy will be $3$ feet below the midline.

Answer to Problem 13.22EP

  $12$ Second.

Explanation of Solution

Given:

The given equation for the height in feet of buoy

  $y=6\cos 30t$

Here, t represents time in seconds.

Calculation:

Since the buoy is at the top of the wave at $0$ second and then be at $3$ feet below the midline, therefore:

  $\begin{array}{l}y=6\\ y=6\cos 30t\\ 6=6\cos 30t\\ 1=\cos 30t\\ \cos 360=\cos 30t\\ 30t=360\\ t=12\end{array}$

Hence, the time taken is $12$ seconds for buoy to be $3$ feet below the midline.