Question

The wheels of the locomotive of a train are 2.1 m in radius. They make 75 revolutions in one minute.

Answer 1

Radius of the wheel =   2.1 m

Circumference of the wheel = 2πr

${\displaystyle =2\times \frac{22}{7}\times 2.1}$

= 13.2 m

Distance covered by the wheel in 1 revolution = 13.2 m

Distance covered by the wheel in 75 revolutions ${\displaystyle =(13.2\times 75)=(990\times \frac{1}{100})\text{m}}$

${\displaystyle =(990\times \frac{1}{1000})\text{km}}$

Distance covered by the wheel in 1 minute = Distance covered by the wheel in 75 revolutions ${\displaystyle =\frac{990}{1000}\text{km}}$

∴ Distance covered by the wheel in 1 hour ${\displaystyle =\frac{990}{1000}\times 60}$

= 59.4 km / h