ANGULAR MASS OR MOMENT OF INERTIA

Equation (i) expresses the angular momentum L of a bicycle wheel as a numerical quantity Mr² times the vector angular velocity . This is not very different from linear momentum which is the mass (M) times the linear velocity vector

.....(i)

.........(1)

We obtain an analogy between linear and angular momentum if we call the quantity (Mr²) the angular mass of the bicycle wheel. Designating the angular mass by the letter I, we get

.........(2)

.........(3)

The quantity I is usually called moment of inertia rather than angular mass, but angular mass provides a better description of what we are dealing with. We will use either name, depending upon which seems more appropriate.