The moments of the components of these actions and reactions in a plane to which the axis of rotation is at right angles are the two aspects of the torque acting, and therefore the torque acting on B through the shaft is measured by the torque required to hold A still.
The counterpoise w balances the head about its axis of rotation.
The axis of rotation AB bears a rigidly attached rod DBC inclined to it at an angle equal to the sun's polar distance.
Take rectangular axes, of which Oz coincides with the axis of rotation.
It is to be carefully noticed that the axis of resultant angular momentum about 0 does not in general coincide with the instantaneous axis of rotation.
