The wheel of a cart is making 5 revolutions per second. If the diameter of the wheel is 84 cm, find its speed in km per hour. [Take π = 22/7]

Diameter of the wheel = 84 cm

Let the radius of the wheel be R cm

Radius of the wheel = 84/2 cm = 42 cm

No. of revolutions wheel makes = 5 rev/sec

Since, 1 revolution = 2πR

Speed of the wheel = 5 × 2πR rev/sec

= 5 × 2 × 22/7 × 42 = 1320 cm/sec

= 13.20 m/sec

= 13.20 × 3600/1000 km/h

= 47.52 km/h

Since, 1 m/sec = 3600/1000 km/h