The law of Gravitation is also called Newton’s universal law of gravitation which is proposed by Sir Isaac Newton. Gravity means attraction between two objects. Gravitation theory was later replaced by Albert Einstein’s theory of relativity.
Galileo Galilei did modern work on the theory of gravity. Galileo did many experiments. In his experiments he observed dropping balls from the Tower of Pisa. In this way, Galileo proved that the acceleration due to gravity is the same for all objects. Galileo played a key role in the formulation of Newton’s theory of gravitation.
In this article we will state and explain Newton’s Law of Gravitation, Importance of Universal Law of Gravitation, Class 9 NCERT Solution, Newton Gravity, Story of Newton’s Apple and the relation between Universal Gravitational Constant and Gravitational Acceleration in details with derived formula.
Table of Contents
What is Gravity?
When we throw the ball or any object from above, it comes back to the earth. This is possible due to the force of gravity. The gravitational force acting between any matter present in the universe and the force acting between those substances is called gravitational force. This law was propounded by Newton. Therefore this law is called Newton’s law of gravity or Newton’s law of universal gravitation.
Story of newton’s Apple
An interesting story of Newton is prevalent behind the discovery of this law. This story is from Newton’s childhood. One day in childhood Newton was playing in his garden. There was an apple tree in that garden. Apple breaks from that apple tree and falls on the ground. Seeing this fallen apple, Newton starts thinking that why did this apple fall on the ground? Why didn’t he go to the sky?
After this incident, he realized that there is such a force acting on the earth which pulls or attracts the object towards itself. To prove this phenomenon, he later researched it and discovered the law of gravity.
Newton’s law of gravitation and Gravitation formula
Law of gravitation is sometimes called the Inverse Square Law of gravity. According to Newton’s law of gravitation, the force of attraction between any two bodies is directly proportional to the product of the masses and inversely proportional to the distance between them.
Let there be two bodies whose masses are “m1″ and “m2″. Both are situated at a distance “R” from each other. Then, as a rule, this formula can be expressed as:
The value of G is G = 6.67 x 10-11 Nm2/Kg2
According to Newton’s law of gravitation, there is a force of attraction between two objects. Similarly, if one of those two bodies is the earth then this force of attraction is called gravity.
Gravity is the force of attraction of the earth by which the earth pulls an object towards its centre. The acceleration due to this force is called the acceleration of gravity, which is denoted by g. Acceleration of gravity (g) does not depend on the size, shape, mass of the object.
The value of g is 9.8m/s2 or about 10m/s2.
Relationship Between Universal Gravitational Constant and Gravitational Acceleration
According to Newton’s second law of motion, the force on a body is equal to the product of its mass and acceleration:
Let the mass of the earth be M and the radius of the earth be r. Another object of mass m is located on the earth. then according to the force of gravity:
g is also called the gravitational force of the earth.
Interesting facts about the value of g (gravity)
- The value of g decreases as we move up or down from the surface of the earth.
- The value of g is maximum at the pole of the earth.
- The value of g is minimum at the equator of the Earth.
- The value of g decreases as the rotational speed of the earth increases.
- The value of g increases as the rotational speed of the earth decreases.
Change in weight due to acceleration due to gravity in a lift
- When the lift goes up, our weight in the lift seems to have increased.
- When the lift goes down, our weight in the lift appears to decrease.
- When the lift moves up or down with the same velocity, there does not seem to be any change in our weight in the lift.
- The lift falls freely if the rope suddenly breaks while it is descending. In such a situation, our weight in the lift is zero. This is called the state of weightlessness.
- When ascending from the lift’s floor, we will pass through the ceiling if the lift’s descending acceleration is larger than the acceleration caused by gravity.