When the two large spheres are rotated to a new position, the torsion balance will vibrate about a new rest position.  

Determination of the Gravitational Constant School Lab Instrument demonstrates the force of gravity between two masses and allows the gravitational constant to be determined. 

The rotary motion is measured using a capacitive differential sensor, which largely suppresses noise and vibration components in the signal.

The apparatus is moved from its rest position by the attraction of the two spheres to two larger lead spheres. 

The gravitational constant can be determined within the space of a single lesson with an accuracy of better than 10%.

For subsequent evaluation, the data can be exported to a spreadsheet. 

Alternatively, the motion can be demonstrated with the aid of a light pointer. 

The core of the apparatus is a torsion pendulum made of a light bar with two small lead spheres, which is suspended horizontally from a thin wire. 

The output is then recorded using a computer. 

Angular resolution: 25 microradians

Torsion wire: Tungsten, 25 µm

Mass of small lead spheres: 15 g

Gravitational attraction: < 10–9 N

Weight: 5 kg 

Period of oscillation: 2–4 mins

Sampling rate: 0.5, 1, 2, 5, 10 samples/s

Mass of large lead spheres: 1 kg

Dimensions: 190 x 180 x 200 mm³