Dhristi JEE 2022-24

What is the Gravitational Force?

This universe has a lot of forces, pushes, and pulls. We are always pulling or pushing something, even if only on the ground. However, it turns out in physics; there are only four fundamental forces in reality from which everything else is derived, whether the strong force, the weak force, the gravitational force or the electromagnetic force.


The gravitational force is that which attracts any two objects with mass. We call this force attractive because it always tries to pull the masses together, but it never pushes them apart. In fact, every object, including we (a human body), is pulling on every other object in this entire universe! This is simply nothing but Newton's Universal Law of Gravitation. Admittedly, we don't have a huge mass, and so, we're not pulling much on those other objects. Moreover, objects that are really far apart from each other do not either pull on each other noticeably. Nevertheless, there is the force, and we can calculate it.


Newton's Universal Law of Gravitation

The Gravitational Force or Newton Gravity or even the gravitational force between two objects Fg is always attractive and depends only on the distance and the masses involved between them. Every object present in the universe attracts every other object with force on a line joining them.


The equation for Newton gravity is given by,

\[Fg=\frac{Gm1m2}{r^{2}}\]

Here, G refers to the gravitational constant, equal to 6.67 × 10 -11 m3/kg.s2

Fg is the gravitational force between masses m1 and m2.

The equation given above is also referred to as the gravitational force between two objects.

The force or Newton’s gravity is inversely proportional to the square of the distance between their centres of mass and directly proportional to their masses' product. This is known as inverse-square law.

For example, if we double the distance between the Moon and the Earth, the attractive force between the both of them would go down (since it is inverse), and it would go down with a factor of 4 instead of 2, because of the square.

It describes both objects falling down and those in a circular orbit, like a satellite around Earth.


Types of Gravity

Isaac Newton has discovered gravity. It is said that he identified it when he saw an apple  falling from a tree, and then he started wondering about the forces of the universe. It is the force; one attracts a body toward the centre of the Earth.


The Acceleration due to  Gravitational Force of Moon 

The acceleration due to the Moon gravity surface is about 1.625 m/s2 and in turn, about 16.6% that on Earth's surface or 0.166 ɡ where g is the acceleration due to gravity on earth. Across the entire surface, the gravitational acceleration variation is about 0.0253 m/s2, which is 1.6% of the acceleration due to gravity. Because weight is always directly dependent upon the gravitational acceleration, particles on the Moon will weigh only 16.6 % (≈ 1/6) of what they weigh on the Earth, in fact.


Characteristics of Gravitational Forces

The main characteristics of Gravitational Forces can be given as:

  • Basically, the gravitational force is a central force that works across the line joining the centres of two bodies.

  • This force is always a long-range force. The force occurs even when we are talking about a considerable distance.

  • It is also a conservative force. This implies the work done by the gravitational force in displacing a body from one point to another and is only dependent on the initial and final positions of the body. Also, it is independent of the path followed.

  • It is essential to know that unlike electrostatic and magnetic forces, the gravitational force is always attractive.

FAQs on Gravitation

1. Explain the Gravitational Anomalies?

Gravitational anomalies are the differences between the observed acceleration of gravity, or free-fall, on a planet's surface. The corresponding value is predicted from a model of the gravity field of the planet. The model is typically based on simplifying assumptions, like that, under its rotational and self-gravitation motion, the planet assumes the ellipsoid figure of revolution. Then, the surface gravity of this reference ellipsoid is given by a simple formula that contains only the latitude and subtraction from observed gravity in the same location yielding the gravity anomaly.

2. Mention the typical example of Gravitational Force in our daily life?

Gravity is the force that pulls anything down to the centre of the Earth. There will be countless examples of gravitational forces. Let us look at some of them down below.

  • Our weight - If there were no gravity, we would weigh nothing

  • An apple falling from a tree - The reason how Issac Newton discovered gravity

  • Kicking a football up in the air, obviously, it comes back down

  • Buildings sticking to the ground

  • Jumping up and down

  • Rain falling from the sky due to gravity

  • All planets forming the solar system - Why the planets are orbiting the Sun is due to its substantial gravitational pull

  • Waves in the sea are mostly formed because of the gravity of the Moon

  • The Milky Way galaxy is spinning because of the enormous gravitational pull of the supermassive black hole in the very centre (which is 4 million times to the mass of the Sun).

3. What is gravitational potential energy?

Gravitational potential energy refers to the energy an object possesses owing to its position in a gravitational field. Gravitational potential energy is commonly used for an object that is near the surface of the earth, a place where the gravitational acceleration is assumed to be at a constant of about 9.8 m/s2. The gravitational potential energy of an object is equal to its weight multiplied by its height.


The understanding of gravitational potential energy comes from the law of gravity. It is basically equal to the work done against gravity to bring a mass to a given point from infinity. The gravitational potential energy near the surface of a planet is negative. 

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