Answer
$s(t)=\sin \dfrac{2t}{\pi}+1$
Work Step by Step
Here, $v= \dfrac{ds}{dt}=\dfrac{2}{\pi} \cos \dfrac{2t}{\pi}$ and thus, the general form of the function is: $s(t)=\sin \dfrac{2t}{\pi}+C$
Since we have $s=1, t=\pi^2$
Therefore, $s=1, t=\pi^2 \implies 1=\sin \dfrac{2 \pi^2}{\pi}+C$
Thus, $C=1$
Hence, $s(t)=\sin \dfrac{2t}{\pi}+1$