Question

A flywheel rotating about a fixed axis has a kinetic energy of 360 J when its angular speed is 30 rads-1. The moment of inertia of the wheel about the axis of rotation is

• A. 0.6 kgm2
• B. 0.15 kgm2
• C. 0.8 kgm2
• D. 0.75 kgm2

Answer 1

Answer: (C)

0.8 kgm2

Answer 2

Flywheel rotating about a fixed axis works on the principle of conservation of angular momentum, to store rotational energy.

The kinetic energy of the flywheel = 360 J, angular speed, ω = 30 rad/s

The relation between kinetic energy, angular speed, and moment of inertia**** is as follows.

K.E. = ½ Iω2

• Where I = **moment of inertia **
• ω = angular speed

Putting the values in the formula, we get

360 = ½ I(30)2

Simplifying the expression.

$I = \dfrac{2 \times 360}{900} = 0.8kg{m^2}$

So, the moment of inertia of the wheel is 0.8 kgm2 when its kinetic energy is 360 Joules.

Hence, the correct option is (C) is 0.8 kgm2.