Answer
The frequency of $0.5$ means that half a cycle is completed each second.
At $t = 1.5~s$, the object is $4$ units below the equilibrium point.
At $t = 2~s$, the object is at the equilibrium point.
At $t = 3.25~s$, the object is $2.83$ units below the equilibrium point.
Work Step by Step
$s(t) = 4~sin~\pi t$
The frequency is the number of cycles per second.
We can find the frequency:
$f = \frac{\omega}{2\pi} = \frac{\pi}{2\pi} = 0.5$
The frequency of $0.5$ means that half a cycle is completed each second.
The function $~~s(t) = 4~sin~\pi t~~$ oscillates between the values of $-4$ and $4$. The equilibrium point is the middle point which is 0.
We can find the position at $t = 1.5~s$:
$s(t) = 4~sin~(1.5\pi) = -4$
At $t = 1.5~s$, the object is $4$ units below the equilibrium point.
We can find the position at $t = 2~s$:
$s(t) = 4~sin~(2\pi) = 0$
At $t = 2~s$, the object is at the equilibrium point.
We can find the position at $t = 3.25~s$:
$s(t) = 4~sin~(3.25\pi) = -2.83$
At $t = 3.25~s$, the object is $2.83$ units below the equilibrium point.