can you please tell me about the Cavendish's Experiment for the determination of G?

Asked by Pawan | 17th Aug, 2015, 09:54: PM

Expert Answer:

Cavendish's apparatus for experimentally determining the value of G consist of light bar of length 'l' with two small lead spheres of mass m each attached at its end.
The bar is suspended horizontally from its middle by a thin wire.Two heavy spheres each of mass M are placed near the small spheres at desired positions. The big spheres are brought close to the small spheres at equal distances, 'd' on the opposite sides. 
Due to the gravitational force, the big spheres attract the near by small spheres by equal and opposite gravitational force and twists the rod to a measurable amount.
Gravitational force on each small sphere is given as:
begin mathsize 12px style straight F equals GMm over straight d squared end style
Gravitational torque on the bar is given as
begin mathsize 12px style GMm over straight d squared cross times straight l end style
Say that the bar is rotated through an angle θ about the axis of the wire.
A restoring force τθ comes into play.
In equilbrium position:
begin mathsize 12px style τθ space equals GMm over straight d squared cross times straight l end style
Knowing the values of other quantities, the value of G is calculated.

Answered by Yashvanti Jain | 19th Dec, 2017, 02:41: PM