Question

A fan rotating with an initial angular velocity of 1000 rev/min is switched off. In 2

seconds, the fan makes 10 revolutions.. Assuming the angular acceleration is

constant, What is the angular speed after those 2 seconds?

Answer 1

Initial angular velocity = 1000 rev/min = 1000×2×π/60 rad/s = 104.72 rad/s

In 2 sec angular displacement = 10 rev = 10×2×π rad = 62.83 rad

Time = t = 2 sec

Displacement,

Or, 62.83 = (104.72×2)+(0.5×4×)

Or, a = (62.83-209.44)/2 = -73.305 rad/s^2

Final velocity , = 104.72 + (-73.305×2) = -41.89 rad/sec negetive velocity is not possible so, final velocity must be zero..