Kinetic energy is the energy of moving objects, including objects that are rotating. The kinetic energy of a rotating object depends on the object’s angular (rotational) velocity in radians per second, and on the object’s moment of inertia. Moment of inertia is a measure of how easy it is to change the rotation of an object. Moments of inertia are represented with the letter I, and are expressed in units of kg∙m2. The unit of kinetic energy is Joules (J). In terms of other units, one Joule is equal to one kilogram meter squared per second squared ().

K = kinetic energy ()

I = moment of inertia (kg∙m2)

ω = angular velocity (radians/s)

Rotational Kinetic Energy Formula Questions:

1) A round mill stone with a moment of inertia of I = 1500 kg∙m2 is rotating at an angular velocity of 8.00 radians/s. What is the stone’s rotational kinetic energy?

a. K = ?? ??? J

2) What is the rotational kinetic energy of a DVD (digital video disc) with a moment of inertia of I = 1.000×10-4 kg∙m2, rotating at an angular velocity of 760.0 radians/s?

a. K = ??.?? J