Answer
$ y= -30 \sin (\pi x)$
Work Step by Step
Amplitude, $ A=-30$; because the velocity $ v $ is negative.
Given: $\omega =\pi $
Now, period, $ P=\dfrac{2 \pi}{\omega}=\dfrac{2 \pi}{\pi }=2$
Hence, the displacement of the particles after $ x $ seconds can be written as:
$ y= -30 \sin (\pi x)$
