Which term describes the difficulty in getting a body to rotate around an axis?

Which term describes the difficulty in getting a body to rotate around an axis?

• A. Moment of inertia
• B. Deceleration
• C. Angular velocity
• D. Body type

Answer: (A)

When a body resists starting or changing its rotation around an axis, that resistance is called moment of inertia. It depends on how much mass the object has and how that mass is distributed relative to the axis of rotation—the farther the mass is from the axis, the greater the inertia. This is why spinning up a heavy wheel is harder than spinning up a lighter one: the torque you apply has to overcome the inertia to produce angular acceleration. In formula form, torque equals moment of inertia times angular acceleration, so larger inertia means you need more torque for the same rate of spin change. Deceleration describes slowing down, angular velocity is the speed of rotation, and body type isn’t the term used to describe rotational resistance.

When a body resists starting or changing its rotation around an axis, that resistance is called moment of inertia. It depends on how much mass the object has and how that mass is distributed relative to the axis of rotation—the farther the mass is from the axis, the greater the inertia. This is why spinning up a heavy wheel is harder than spinning up a lighter one: the torque you apply has to overcome the inertia to produce angular acceleration. In formula form, torque equals moment of inertia times angular acceleration, so larger inertia means you need more torque for the same rate of spin change. Deceleration describes slowing down, angular velocity is the speed of rotation, and body type isn’t the term used to describe rotational resistance.