Answer
3 cm/sec
Work Step by Step
We know that if point $P$ is a point on a circle of radius $r$, and $P$ moves in a distance $s$ on the circumference of the circle in an amount of time $t$, then the linear velocity, $v$, of $P$ is calculated as $v=\frac{s}{t}$.
We are given that $s=12$ cm and $t=4$ sec.
Therefore, $v=\frac{12cm}{4sec}=\frac{12cm\div4}{4sec\div4}=\frac{3cm}{1sec}=3$ cm/sec.