What is the measure of an object's resistance to angular acceleration called?

The measure of an object's resistance to angular acceleration is known as the moment of inertia. This concept is crucial in rotational dynamics, as it quantifies how difficult it is to change an object's rotational state. The moment of inertia depends not only on the mass of the object but also on how that mass is distributed relative to the axis of rotation. It can be thought of as the rotational equivalent of mass in linear motion, representing the object's resistance to changes in its rotational motion.

For example, when a solid disk and a hollow disk of the same mass and radius are spun, the hollow disk will have a larger moment of inertia due to its mass distribution being farther from the axis, thereby requiring more torque to achieve the same angular acceleration as the solid disk. This illustrates the importance of understanding moment of inertia in mechanical and engineering applications, particularly in analyzing rotational systems.

In contrast, inertia refers to the resistance of any physical object to any change in its state of motion or rest, angular momentum is a measure of the amount of rotation an object has, and torque is the rotational equivalent of force, defining the tendency of a force to produce rotation about an axis. Each of these concepts plays a role in understanding rotational dynamics, but moment of inertia is specifically the term