Answer
a. $20\ cm$
b. $\frac{1}{8}\ Hz$ (cycles per second)
c. $8\ sec$.
Work Step by Step
a. The maximum displacement is the same as the amplitude, which is $20\ cm$ based on the given equation.
b. The frequency $f$ can be found from the given equation as $\omega=2\pi f=\frac{\pi}{4}$; thus $f=\frac{1}{8}\ Hz$ (cycles per second)
c. The time required for one cycle is the same as the period, which is $p=\frac{1}{f}=8\ sec$.
