Question

A fan is rotating with angular velocity $100rev/sec$. Then it is switched off. It takes $5$ minutes to stop. Find the average angular velocity during this interval.

• A. $100rev/sec$
• B. $75rev/sec$
• C. $125rev/sec$
• D. $50rev/sec$

Answer 1

The correct option is D $50rev/sec$

Given, Initial angular velocity, ${\omega }_0=100rev/s$

Final angular velocity, $\omega =0rev/s$

$\therefore$ Total number of revolution made by fan, $\theta =(\frac{\omega +{\omega }_0}{2})t=\frac{0+100}{2}\times 5\times 60=15000rev$

$\therefore$ Average angular velocity in this interval,$=\frac{15000}{5\times 60}=50rev/sec$