Question

A fan is making $600rpm$. If it makes $1200rpm$, what is the increase in its angular velocity?

• A. $10\pi rad{s}^{-1}$
• B. $20\pi rad{s}^{-1}$
• C. $60\pi rad{s}^{-1}$
• D. $40\pi rad{s}^{-1}$

Answer 1

Answer: (B)

$20\pi rad{s}^{-1}$

$\omega =600\times \frac{2\pi }{60}=20\pi rad/s$

$\omega$ is doubled if it takes $1200rpm$
${\omega }_0=\frac{1200\times 2\pi }{60}$$=40\pi rad/s$
$\therefore \Delta \omega ={\omega }_0-\omega$ $=20\pi rad/s$