Apparatus for investigating frictionless rotation. A small rotating disc with a protractor scale supports a cross bar to which weights can be attached. The disc is supported by a bed of air in which its axis is centred. A driving weight is suspended from a hook at the end of a string that is passed over a single pulley on one side and a multiple pulley on the other. The rotation is very slow and can be measured using a stopwatch by hand. Alternatively, a digital timer may be used. This can be started by a mechanism that is supplied with the kit and halted by a signal from a laser reflection sensor when the wheel passes through angle zero.
Rotational motion: uniform and under constant acceleration
Newton's equations of motion for rotational motion
Moment of inertia and torque
Moment of inertia as determined by experiment
Simple harmonic motion of rotating objects
Protractor scale: 0 – 360°
Scale divisions: 1°
Length of cross bar: ca. 440 mm
Radii of perforations: 30 – 210 mm
Separation of perforations: 20 mm
Radii of multiple pulley: 5.0 mm/10.0 mm/15.0 mm
Moment of inertia of
disc with cross bar: 0.16 g m2 approx.
Maximum moment of inertia: 7.1 g m2 approx.
Minimum driving torque: 0.05 mN m approx.
Maximum driving torque: 0.60 mN m approx.
1 Air bed
1 Rotating disc with cross bar
1 Multiple pulley
1 Release mechanism
2 S-shaped hooks 1.00g
1 S-shaped hook 2.00 g
1 Set of weights (2x 12.5 g, 2x 25 g, 2x 50 g)
1 Compressor for connection to mains
1 Silicon tubing with by-pass valve (not illustrated)
1 Stand rod with 3 securing screws and 2 screws for levelling