As you may have realized by now balancing is FUN^2.

We now understand that the main reason for balancing is to reduce the bearing load and bearing vibration to acceptable levels. Balancing also produces a reduction in noise due to the reduction in vibration. Unbalance robs power from the system that is dissipated in the form of vibration and noise and can cause other problems like stator rub and early bearing failure.

The unbalance does not change with speed but the effect does. Centrifugal (outward) force is proportional to the square of the speed.

The balancing machine measures the amount and angle of the unbalance so it can be corrected by adding, removing or moving mass.

We use mass since we are not talking gravity (apples falling on heads) but rotational conditions that are the same on Earth, Mars, Jupiter, or in deep space.

Balancing is the correction of the rotor mass distribution of the rotor relative to the defined rotational axis.