Question

A motorcar is running at the rate of 66 km per hour. Each

of its wheels makes 500 revolutions per minute. Find the
radius of the wheel.
.(Ans: 35 cm)
​

Answer 1

Given:

The radius of a wheel =r=35 cm=0.35 cm.

The speed it must keep =s=66 km/h=

60

66×1000

m/min=1100 m/min

To find out:

The number of revolution =n, it makes per minute to maintain that speed.

Solution:

The circumference =C of the wheel =2πr=2×

7

22

×0.35 m=2.2 m=C

The distance the wheel covers in 1 min=d=1100 m.

Now the distance =d covered by a wheel in one revolution = the circumference of the wheel.

∴ Here the number of revolution =n=

C

d

=

2.2

1100

=500.