# Rotational Inertia Formula

The rotational inertia is defined as an analog of mass in the case of linear motion. It describes the relationship under dynamics of rotational motion. The moment of inertia needs to be specified with respect to a chosen axis of rotation.It depends on the shape of the object and the axis of rotation. The rotational inertia differs for different objects and varies according to its rotational axis.

The rotational inertia formula is given by,

I = mr2

Where,

I = rotational inertia,

m = mass of the object,

r = radius of the circular path.

Example 1

Determine the rotational inertia if a 10kg object is rotating around a circular path of radius 7m?

Solution:

Given:

m = 10kg

r = 7m

Rotational inertia Formula is given by,

I = mr2

= 10 × 72

= 490kgm2

Example 2

An object of mass 3kg is rotating a circular path of radius 10m. Calculate the rotational inertia of the object.

Solution:

Given:

m = 3kg

r = 10m

Rotational inertia Formula is given by,

I = mr2

= 3 × 102

= 130kgm2