A flywheel's diameter is twice that of another of the same shape and mass. Rotational inertia of the larger flywheel is
A)two times greater.
B)four times greater.
C)the same as the other's.
D)half.

Question

Quizplus · Accepted Answer

The rotational inertia of a flywheel depends on its mass and the distribution of that mass around the axis of rotation. Since the two flywheels have the same shape and mass, the larger flywheel will have more mass distributed farther from its axis of rotation, thus increasing its rotational inertia. The rotational inertia of a flywheel is proportional to the square of its radius, so if the diameter of the larger flywheel is twice that of the smaller flywheel, then its radius is also twice as long, resulting in a four-fold increase in rotational inertia. Therefore, the correct answer is B - four times greater.

A Flywheel's Diameter Is Twice That of Another of the Same