Question

The diameter of a wheel of a bus is 90cm which makes 315 revolutions per minute. Determine its speed in kilometer per hour.

Answer 1

Diameter of wheel =90cm

⇒ Radius of wheel (r)=

2

90

cm=45cm

⇒ Distance covered in 1 revolution =2πr

⇒ Distance covered in 1 revolution =2×

7

22

×45=

7

1980

cm

⇒ Distance covered in 315 revolutions =

7

1980

×315=89100cm=891m

⇒ Hence, the speed is 891m/min=

1000

891

×60km/hr=53.46km/hr..