What is the difference between 'G' and 'g'?

The capital 'G' stands for the Universal Gravitational Constant, a fundamental constant of nature with a fixed value of approximately $6.674 imes 10^{-11} , ext{N m}^2/ ext{kg}^2$. It quantifies the strength of the gravitational interaction between any two masses in the universe. The lowercase 'g' represents the acceleration due to gravity, which is the acceleration experienced by an object due to the gravitational pull of a celestial body (like Earth). Its value is approximately $9.8 , ext{m/s}^2$ on Earth's surface but varies with altitude, latitude, and the mass/radius of the planet. 'G' is universal and constant, while 'g' is specific to a location and celestial body.

Why is gravitational force considered a weak force?

Gravitational force is considered weak because the Universal Gravitational Constant 'G' is an extremely small number ($6.674 imes 10^{-11} , ext{N m}^2/ ext{kg}^2$). This means that for everyday objects with relatively small masses, the gravitational force between them is negligible and imperceptible. For gravity to become significant and noticeable, at least one of the interacting objects must have an enormous mass, like a planet or a star. Compared to the electromagnetic force, which can easily lift objects against Earth's gravity, gravity is indeed the weakest of the four fundamental forces.

Does the Universal Law of Gravitation apply to objects of all sizes?

Yes, the Universal Law of Gravitation applies to objects of all sizes, from subatomic particles to galaxies. However, its effects are most prominent and easily observable when at least one of the interacting objects has a very large mass, such as planets, stars, or black holes. For microscopic particles, other fundamental forces (like the strong nuclear force and electromagnetic force) are far more dominant. Despite this, the underlying principle of gravitational attraction based on mass and distance holds true universally.

How does the inverse square law affect gravitational force?

The inverse square law states that the gravitational force is inversely proportional to the square of the distance between the centers of the two masses ($F propto 1/r^2$). This means that as the distance between objects increases, the gravitational force decreases very rapidly. For example, if you double the distance, the force becomes one-fourth of its original value. If you triple the distance, the force becomes one-ninth. This rapid decrease explains why the gravitational influence of distant objects quickly becomes negligible and why gravity is a 'short-range' dominant force in local systems but can act over vast cosmic distances due to immense masses.

Can gravitational force be repulsive?

No, according to Newton's Universal Law of Gravitation, the gravitational force is always attractive. It always pulls objects towards each other, never pushes them apart. This is a key distinguishing feature from other fundamental forces like the electromagnetic force, which can be both attractive (between opposite charges) and repulsive (between like charges). The attractive nature of gravity is what causes objects to fall, planets to orbit stars, and galaxies to hold together.

What is the role of the Universal Gravitational Constant (G)?

The Universal Gravitational Constant (G) is a proportionality constant that converts the product of masses and inverse square of distance into the actual magnitude of the gravitational force. It essentially sets the 'strength' of gravity. Without G, the formula $F = rac{m_1 m_2}{r^2}$ would only give a proportional relationship. G makes it an equality and allows us to calculate the force in standard units (Newtons). Its extremely small value highlights why gravity is the weakest of the four fundamental forces, requiring immense masses to produce significant effects.

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Version 1Updated 22 Mar 2026

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Sir Isaac Newton's Universal Law of Gravitation, first published in his 'Philosophiæ Naturalis Principia Mathematica' in 1687, posits that every particle in the Universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This fundamental law describes the gravitation…

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The Universal Law of Gravitation, proposed by Newton, states that every particle in the universe attracts every other particle with a force directly proportional to the product of their masses ( $m_1 m_2$ ) and inversely proportional to the square of the distance ( $r^2$ ) between their centers.

Mathematically, this is expressed as $F = G \frac{m_1 m_2}{r^2}$ . Here, $G$ is the Universal Gravitational Constant, a fixed value of $6.674 \times 10^{-11} ,\text{N m}^2/\text{kg}^2$ , which signifies the inherent weakness of gravity.

The force is always attractive and acts along the line joining the centers of the two masses. This law is fundamental to understanding planetary motion, satellite orbits, and the acceleration due to gravity ( $g = G \frac{M}{R^2}$ ), which varies with the celestial body and location, unlike the constant $G$ .

The principle of superposition allows us to calculate the net gravitational force on an object due to multiple other objects by vectorially adding individual forces.

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Universal Law of Gravitation: —

F = G \frac{m_1 m_2}{r^2}

Universal Gravitational Constant (G): —

6.674 \times 10^{-11} ,\text{N m}^2/\text{kg}^2

(scalar, universal, independent of medium)

Acceleration due to Gravity (g): —

g = G \frac{M}{R^2}

(vector, varies with location, depends on planet's mass

M

and radius

R

)

Nature of Force: — Always attractive, acts along the line joining centers.

Inverse Square Law: —

F propto 1/r^2

. If

r

doubles,

F

becomes

F/4

Superposition Principle: — Net force is vector sum of individual forces.

Weakest Fundamental Force.

To remember the formula $F = G \frac{m_1 m_2}{r^2}$ : For Gravity, Many Masses Radiate Strongly. (F = Force, G = Gravitational constant, M = Mass, R = Radius/distance, S = Square - for $r^2$ )

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