3.21: Perpendicular from centre to a chord through a diameter point

The diagram shows a circle, centre $O$, radius $10\text{ cm}$. The points $A$, $B$ and $P$ lie on the circumference of the circle. The chord $AB$ is of length $14\text{ cm}$. The point $Q$ lies on $AB$ and the line $POQ$ is perpendicular to $AB$.