Question

A ceiling fan is rotating with an angular velocity of $10rad/s$. It takes $40s$ to stop when it is switched off. The average angular velocity during this interval is (assume uniform angular retardation)

• A. $5rad/s$
• B. $4rad/s$
• C. $2rad/s$
• D. $-5rad/s$

Answer 1

The correct option is A $5rad/s$

Given initial angular velocity ${\omega }_0=10rad/s$
Final angular velocity $\omega =0$

Since angular retardation is constant.
Average angular velocity is given by
${\omega }_{avg}=\frac{{\omega }_0+\omega }{2}$
$=\frac{10+0}{2}=5rad/s$