a kinetofrictional force testing apparatus has a spindle rotated by a variable speed motor . a load cell is disposed in opposition to a disk coupled to the spindle and includes a test head for the disk , a rotational frequency controlling synthesizer , and a personal computer for general control . the rotational speed of the motor is varied on the basis of clock pulses from the rotational frequency controlling synthesizer associated with the personal computer . the rotational frequency and rotational acceleration / deceleration of the disk coupled to the spindle are digitally controlled by a predetermined program set in the personal computer . the test head is supported by a leaf spring having strain gauges mounted on its lateral surfaces . frictional forces are measured by the output of the strain gauges .