Moment of inertia measures an object's resistance to changes in what?

• A. Changes in rotation velocity
• B. Changes in linear velocity
• C. Changes in temperature
• D. Changes in mass

Answer: (A)

Moment of inertia describes how hard it is to change an object's rotational motion, specifically its angular velocity, when a torque is applied. The relation τ = Iα shows that for a given torque, a larger I produces a smaller angular acceleration, so the rotation speed changes more slowly. Mass distribution matters: more mass farther from the axis increases I and makes changes in rotation harder; mass closer to the axis lowers I and allows faster changes in rotation. A classic example is a figure skater pulling in their arms to spin faster, which reduces I and increases angular velocity for the same angular momentum. This concept does not describe resistance to changes in linear velocity, temperature, or mass.