Concepts and definitions:

- Cavendish Experiment:

• It was an experiment conducted in 1797-98 by British scientist Henry Cavendish to measure the gravitational constant.
• The experiment involved measuring the very tiny force of attraction between two lead balls of known mass.
• From this measurement, Cavendish calculated the value of the gravitational constant accurately.

- Repulsion and Attraction:

• Repulsion: Force of repulsion occurs when bodies having the same charge interact with each other.

• **Attraction**: Force of attraction occurs when two bodies having opposite charges interact with each other.
  

- Torsion Balance:

• A torsion balance is a sensitive instrument that measures tiny torsional forces (twisting forces) acting on a suspended fiber or wire.

• It consists of a suspended horizontal beam with two masses attached to its ends, and a graduated circular scale to measure the angle of rotation of the beam when a force is applied.

- Newton’s Law of Gravitation:

• This law describes the force of attraction between any two objects with mass in the universe.
• The law states that every particle of matter in the universe attracts every other particle with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

- Gravitational Constant:

• The gravitational constant, denoted by (G), is a fundamental physical constant that appears in Newton’s law of gravitation.
• It represents the proportionality factor between the gravitational force between two objects and the product of their masses and the square of the distance between them.