Question

The diameter of the wheels of a bus is 140cm. How many revolutions per minute must a wheel make to move at a speed of 66km per hour?

Answer 1

Distance covered in 1 revolution = Circumference of wheel

= 2πr

= 2 × π × 70

= 140π cm

Now, we find total distance covered

We know that,

Speed = Distance/Time

Here, Speed = 66 km/hr

Time = 1 minutes

= 1/60 hour

Putting a value in the formula, we get

66 = Distance/1/60

Distance = 66/60

 

⇒ Distance = 1.1 km

= 1.1 × 1000 m

= 1100 m

= 1100 × 100 cm

= 110000 cm

Now,

Number of revolutions = 250