Question

A boy is cycling such that the wheels of the cycle are making 140 revolutions per minute. If the diameter of each wheel is 60 cm. Calculate the speed which the boy is cycling.

Answer 1

Given:

Wheels make 140 revolutions per minute (140 r/min).

Diameter of each wheel = 60 cm.

Step-wise calculation:

1. Circumference of wheel

= π × Diameter 

= π × 60 cm

= 60π cm

= 0.6π m

2. Distance travelled in 1 minute

= Revolutions × Circumference

= 140 × 0.6π m

= 84π m

3. Distance travelled in 1 hour

= 84π m/min × 60 min 

= 5040π m

= 5.04π km

4. Numerical value (Take π = 3.1416):

Speed = 5.04 × 3.1416

= 15.84 km/h   ...(In m/s: 15.84 ÷ 3.6 = 4.40 m/s.)

The boy is cycling at approximately 15.84 km/h (≈ 4.40 m/s).