A wheel of radius 2.1 m of a vehicle makes 75 revolutions in 1 min

A wheel of radius 2.1 m of a vehicle makes 75 revolutions in 1 min. What is the speed of the vehicle?

  1. 59.4 km/h
  2. 78 km/h
  3. 37.4 km/h
  4. 35.4 km/h

Answer

Distance traveled in 1 revolution = 2πr, where r is the radius = 2.1 m

 So, distance traveled in 75 revolutions = 2π × 2.1 × 75 = 990 m = 0.99 km

Time = 1 min = 1/60 h

So, required speed = 0.99/(1/60) km/h = 59.4 km/h

The correct option is A.