Question

Find the average angular speed of the minute hand of a normal clock in $1.5\text{hrs}$.

• A. $\frac{\pi }{3600}\text{rad/s}$
• B. $\frac{\pi }{1800}\text{rad/s}$
• C. $\frac{\pi }{900}\text{rad/s}$
• D. $\frac{3\pi }{1800}\text{rad/s}$

Answer 1

The correct option is B $\frac{\pi }{1800}\text{rad/s}$

$1.5\text{hrs}=90\text{min}$. Minute hand completes one revolution in $60\text{min}$
We know that the average angular speed is given by
$\overline{\omega }=\frac{\Delta \theta }{\Delta t}$
$\Rightarrow \overline{\omega }=\frac{\frac{2\pi }{60}\times 90\text{rad}}{90\times 60sec}=\frac{\pi }{1800}\text{rad/s}$