A heavy flywheel rotating at 1500 rpm experiences a constant frictional torque. It slows down to 900 rpm in 12 s . How much additional time will it take for the flywheel to come to a complete stop?

Step-by-step solution

Let the constant angular retardation be . Using the first equation of rotational motion, = ₀ - t . For the first interval: Initial angular speed, ₀ = 1500 rpm Final angular speed, = 900 rpm Time, t = 12 s The rate of decrease of angular speed is: = 1500 - 900 12 = 600 12 = 50 rpm s ⁻¹ . For the second interval, the flywheel slows down from 900 rpm to rest ( 0 rpm ). The additional time t' required is: t' = 900 - 0 = 900 50 = 18 s . Answer: 18 s