What is the Gravitational Constant? Definition & Facts

Introduction

Gravity refers to the force of attraction that occurs between two bodies. It is also called gravitation. The force of gravity is a fundamental force present in the entire universe. It is responsible for maintaining the physical connection between matter and space. Along with electromagnetic and nuclear forces, the gravitational force is also an important force present in the universe.

Gravitational force acts on all objects that have mass or energy.

The Concept of Gravity

The concept of gravity or the gravitational force was first discovered by Sir Isaac Newton in 1697. He described the motions of heavenly bodies in the universe such as planets and moons.

Newton’s Law of Gravitational Constant

• The Gravitational Constant is also known as the Universal Gravitational Constant or the Newtonian Constant of Gravitation.
• The Gravitational Constant is denoted by the English alphabet capital letter G.
• G is known as a universal constant as its value does not depend on any physical variable.
• The universal law of Gravitation states every object in the universe attracts every other object with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them.
• Thus, The magnitude of the force acting between two point masses is directly proportional to the product of their masses and the magnitude of the force acting between two point masses decreases rapidly as distance increases.

where F is the gravitational force between the two bodies, m₁ represents the mass of one of the objects, m₂ represents the mass of the second object, and r represents the distance between the centres of the two objects. G represents the universal gravitational constant.

Importance of Gravitational Constant and The Universal Law of Gravitation

The universal law of gravitation explained various phenomena that occur in nature, such as

• The motion of planets around the sun in our solar system.
• The motion of the moon around the sun.
• The force that is responsible for binding us to the earth.
• The reason for the occurrence of tides due to the sun and the moon.

Value and Uncertainty

• The Gravitational Constant is difficult to measure with high accuracy, as the gravitational force is characterized as an extremely weak force as compared to other fundamental forces.
• The most recommended value of the Gravitational Constant is
• It represents the SI unit of the Gravitational Constant.

Free Fall

• When an object falls towards the earth and no other forces except the gravitational force are acting upon it, we say that the object is in free fall.

Mass and Weight

• The mass of an object is defined as the measure of its inertia. If the mass of an object is greater, the inertia is also greater. The mass of an object remains the same whether the object is on the moon, the earth, or even in any part of space. Thus, the mass of an object does not change from place to place and is constant.
• The weight of an object is related to the force with which the object is attracted toward the earth. So, the SI unit of weight is the same as the SI unit of Force, that is, Newton (N).
• The force acting vertically downwards describes the weight of an object. Hence, the weight has both magnitude and direction and is a vector quantity.
• Weight is equal to the mass of the object multiplied by the acceleration due to gravity.

W = mg

Here, W is the weight of the object, m is the mass of the object and g is the acceleration due to gravity.

• The value of g is constant at a given place.
• The mass of an object is the same everywhere whereas, the weight of an object depends on its location as the value of g depends upon the location.

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