Variable inertia bar rvfm p10713 p this apparatus helps to demonstrate that the torque required to accelerate a flywheel depends upon its moment of inertia rather than its mass p p a steel bar 790 x 12mm is mounted at its centre on a sleeved spindle the spindle is extended through a sleeve so that the bar may be rotated by a weight and string heavy adjustable masses are mounted on each end of the bar and may be clamped at any desired position enabling inertia to be varied p rvfm varia