Question

A sphere of mass 15 kg and radius 0.75 m rotates about a tangent. The moment of inertia of the sphere is:

• A. $15kg-m^2$
• B. $11.8kg-m^2$
• C. $13kg-m^2$
• D. $9kg-m^2$

Answer 1

The correct option is B $11.8kg-m^2$

Moment of inertia of a solid sphere about the diameter is $2M{R}^2/5$
Moment of inertia of the solid sphere about its tangent is obtained using parallel axis theorem.= $2M{R}^2/5+M{R}^2=7M{R}^2/5$
Substituting the values of M and R, we get, $I=7\times 15\times {0.75}^2/5=11.81$
Thus the correct options is (b)