A boy and a girl are riding on a merry-go-round that is turning. The boy is twice as far as the girl from the merry-go-round's center. If the boy and girl are of equal mass, which statement is true about the boy's moment of inertia with respect to the axis of rotation?
A) The boy has a greater moment of inertia, but it is impossible to say exactly how much more.
B) His moment of inertia is twice the girl's.
C) His moment of inertia is 4 times the girl's.
D) The moment of inertia is the same for both.
E) His moment of inertia is half the girl's.

Question

Quizplus · Accepted Answer

The moment of inertia depends on the mass and the square of the distance from the axis of rotation. Since the boy is twice as far from the center, his moment of inertia is $2^2 = 4$ times greater than the girl's.

A Boy and a Girl Are Riding on a Merry-Go-Round