# The rotational inertia of a disk about its axis is 0.70kgm2. When a 2kg mass is added to its rim ,0.40m what will be its rotational inertia?

Aug 7, 2018

The moment of inertia is $= 1.02 k g {m}^{2}$

#### Explanation:

The moment of inertia of the disc about the axis $O$ is

${I}_{O} = 0.7 k g {m}^{2}$

The moment of inertia of the mass is

${I}_{m} = m {r}^{2} = 2 \cdot {0.4}^{2} = 0.32 k g {m}^{2}$

The total moment of inertia is

$I = {I}_{O} + {I}_{m} = 0.7 + 0.32 = 1.02 k g {m}^{2}$