Question

A boy is cycling such that the wheels of the cycle are making $140$ revolutions per minute. If the diameter of the wheel is $60cm$, then find the speed per hour with which the boy is cycling.

Answer 1

Radius of wheel, $r=\frac{diameter}{2}=\frac{60}{2}=30$cm

In one revolution, wheel covers a distance $=2\pi r=60\pi$ cm

$\Rightarrow$ In one minute, wheel covers a distance $=60\pi \times 140$cm

$\Rightarrow$ Speed $=\frac{Distance}{time}=\frac{6\pi \times 14}{60}msec=\frac{22}{7}\times 14=4.4m{\sec }^{-1}$.