Question

The wheel of a motor cycle is of radius $35cm$. The number of revolutions per minute must the wheel make so as to keep a speed of $66km/h$ is

• A. $1100$
• B. $600$
• C. $500$
• D. $44$

Answer 1

The correct option is C $500$

Given:

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

The speed it must keep $=s=66km/h=\frac{66\times 1000}{60}m/min=1100m/min$

To find out:

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

Solution:

The circumference $=C$ of the wheel $=2\pi r=2\times \frac{22}{7}\times 0.35m=2.2m=C$

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

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

$\therefore$ Here the number of revolution $=n=\frac{d}{C}=\frac{1100}{2.2}=500.$