Question:
A block hangs from a string wrapped on a disc of radius $20 \mathrm{~cm}$ free to rotate about its axis which is fixed in a horizontal position. If the angular speed of the disc is $10 \mathrm{rad} / \mathrm{s}$ at some instant, with what speed is the block going down at the instant?
Solution:
Block speed=Rim speed of the disc $\mathrm{v}=\mathrm{R} \omega=(0.2)(10)$
$v=R \omega=(0.2)(10)$
$v=2 \mathrm{~m} / \mathrm{s}$