Answer
$$1.257 \mathrm{\ sec},\quad 0.796 \mathrm{\ Hz}$$
Work Step by Step
$\because$ we can describe displacement of a certain object by:
$$y(t)=23 \sin (5 t)$$
Where $t$ measured in Seconds.
$$\therefore \omega=5\ rad/sec \quad\quad\quad\quad(1)$$
we can get Its period by:
$$P=\frac{2 \pi}{\omega} \quad\quad\quad\quad(2)$$
Substitute from $(1)$ in $(2) :$
$$\therefore P=\frac{2 \pi}{5}=1.257 \mathrm{sec}\quad\quad\quad\quad(3)$$
we can get the oscillation frequency by:
$$f=\frac{1}{P}$$
Substitute the value of $P$ calculated in $(3) :$
$$\therefore f=\frac{1}{1.257}=0.796 \mathrm{Hz}$$
