A flywheel turning at 1200 rev/min (125.7 rad/s) constant angular velocity has a radius of 2.5 cm. As it turns, a string is to be wound onto its rim. How long is the string if it is wound up in 10 seconds?

Question

It says the answer is 31.4m, but I don't know the equations to get this answer.

Answer 1

10 seconds is 1/6 minute, so that would be 200 revolutions
The circumference of the rim is 2pi*r = 5pi cm
200*5pi = 1000pi = 3141.6 cm = 31.4m