Moment of inertia: A uniform solid sphere has a moment of inertia I about an axis tangent to its surface. What is the moment of inertia of this sphere about an axis through its center?
A) 1/7 I
B) 2/7 I
C) 2/5 I
D) 3/5 I
E) 7/5 I

Question

Quizplus · Accepted Answer

The moment of inertia of a solid sphere about an axis through its center is (2/5)MR². Using the parallel axis theorem, the moment of inertia about a tangent axis is I = (2/5)MR² + MR² = (7/5)MR². Therefore, the moment of inertia about the center is (2/5)/(7/5) = 2/7 of the tangent axis moment of inertia.

Moment of Inertia: a Uniform Solid Sphere Has a Moment