Question

A flywheel in the form of a solid circular disc of radius 100 mm and uniform thickness has a mass of 10 kg. If it is rotating at a uniform angular velocity of 20 rad/s, the kinetic energy (in J) of the flywheel is _______.

Answer 1

Concept:

Flywheels

A flywheel is used to control the variation in speed during each cycle of the engine.

The kinetic energy of the flywheel can be calculated by:

\(KE= \dfrac{1}{2}I{ω ^2}\)

where

I = moment of inertia of thin disc = 0.5 × mR2

ω = angular velocity of the flywheel 

Calculation:

Given:

Mass of flywheel (m) = 10 kg, radius (R) = 100 mm = 0.1 m, ω = 20 rad/s

I = 0.5 × mR2

I = 0.5 × 10 × 0.12

I = 0.05 kg.m2

The kinetic energy of the flywheel is:

\(KE= \dfrac{1}{2}I{ω ^2}\)

\(KE=\dfrac12× 0.05×20^2=10~\rm Joule\)