According to the Henry Cavendish experiment conducted in 1797-1798, what was the value of the universal constant of gravity?

6.75 × 10^-11 Nm² /kg²

The correct answer is option 3. 6.75 × 10^-11 Nm² /kg².

The Henry Cavendish experiment, conducted between 1797 and 1798 by the British scientist Henry Cavendish, was pivotal in determining the value of the universal constant of gravity, denoted by \( G \). The experiment aimed to measure the gravitational force between two masses in a laboratory setting.

In Cavendish's experiment, a torsion balance was utilized. This apparatus consisted of a horizontal bar suspended from a thin wire, with two small lead spheres attached to each end of the bar. Larger lead spheres, known as "attracting masses," were positioned near the smaller spheres, causing a gravitational attraction between them. The torsion balance was designed to measure the twisting of the wire caused by this gravitational attraction.

By carefully measuring the angular deflection of the torsion balance, Cavendish was able to calculate the gravitational force between the masses. This force was proportional to the product of the masses and inversely proportional to the square of the distance between them, in accordance with Newton's law of universal gravitation.

From his experimental measurements, Cavendish determined the value of the gravitational constant \( G \), which represents the strength of the gravitational force between two objects with unit mass separated by a unit distance. The value he obtained was approximately \( 6.75 \times 10^{-11} \, \text{Nm}^2/\text{kg}^2 \).

This value of \( G \) remains fundamental in physics and is used in various fields, including astronomy, geophysics, and engineering. It allows for the calculation of gravitational forces between celestial bodies, the determination of planetary orbits, and the understanding of the behavior of gravitational fields in different contexts. Cavendish's experiment laid the foundation for our modern understanding of gravity and its role in the universe.