Here \(\omega\) is the Greek letter omega, and the \(z\) in the subscript tells us that the blade is rotating around an axis that we call the \(z\) axis (Figure 8-3). For any rotating rigid object, the value of \(\omega_\mathrm{average}\), \(z\) is the same for all pieces of the object. The average angular velocity can be positive or negative, depending on the direction in which the object rotates. A common choice is to take counterclockwise rotation to be positive and clockwise rotation to be negative, but the choice is up to you.