Question:
A disc of radius $10 \mathrm{~cm}$ is rotating about its axis at an angular speed of $20 \mathrm{rad} / \mathrm{s}$. Find the linear speed of
(a) a point on the rim.
(b) the middle point of a radius.
Solution:
$(a) v=r w=(0.1)(20)$
$v=2 \mathrm{~m} / \mathrm{s}$
(b) $v=r \omega=\left(\frac{0.1}{2}\right)(20)$
$v=1 \mathrm{~m} / \mathrm{s}$