Question

Define gravitational constant G.

Answer 1

Gravitational constant is a very important concept in physics. The value of gravitational constant is fixed and is used directly in the equations, the value should be known so that it can be used directly. If the concept of gravitational constant is known along with its value, then it becomes easy to define the term.

Complete solution:
The gravitational constant (also known as the universal gravitational constant), denoted by the letter G, is a physical constant involved in the calculation of gravitational effects in Sir Isaac Newton's law of universal gravitation and in Albert Einstein's general theory of relativity.

In Newton's law, it is the proportionality constant that connects the gravitational force between two bodies with the product of their masses and the inverse square of their distance. In the Einstein field equations, it quantifies the relation between the geometry of space, time and the energy–momentum tensor (also referred to as the stress–energy tensor).

The measured value of the constant is known with some certainty to four significant digits. In SI units, its value is approximately $G=6.674\times {{10}^{-11}}\,{}^{N.\,{{m}^{2}}}/{}_{k{{g}^{2}}}$.

The gravitational constant is a defining constant in some systems of natural units, particularly geometrized unit systems, such as Planck units and Stoney units. When expressed in terms of such units, the value of the gravitational constant will generally have a numeric value of 1 or a value close to it. Due to the significant uncertainty in the measured value of G in terms of other known fundamental constants, a similar level of uncertainty will show up in the value of many quantities when expressed in such a unit system.

Note:
Gravitational constant is a term that is widely used in physics and many concepts depend on this constant for its value. Gravitational constant is represented by G, it should not be confused with gravity, as it is represented by g, both the terms are different and are used in different contexts from one another.