Question

a fan makes 600 revolutions per minute if after some time it makes 1200 revolutions then the increase in its angular velocity

Answer 1

20
$\pi$
per second

Answer 2

$u \: = \: 2\pi(n_2 - n_1) \\ \\ = \frac{2\pi \times 600}{60} \\ \\ = 20\pi$