As all we know that, every object is in its fixed position like in our room or class. The benches or table in our class are at the same position always till we cannot apply external force on them. As we apply some external force on them then only, they get moved. Then which magic is happening to remain them on the earth not in the air. All the things are attracting towards earth are only due to the gravitational force which is acting on the all the objects by the earth. The gravitational force acting on each object is different and it can be explained with help of Newton’s law of Gravitation.
Statement:
According to Newton’s law of gravitation every particle of matter or object attracts every other particle of matter or object with some attractive force and which is directly proportional to the product of the masses of the objects and the same attracting force is inversely proportional to the square of the distance between the objects.
Explanation:
- If M1 and M2 is the masses of the objects which are separated by distance r then mathematically, the force of gravitation between then F is given by
F α M1 *M2
F α 1/r2
Thus, F α M1*M2/r2
And F = GM1*M2/r2
Where G is the constant which is called as the universal gravitational constant and its value is 6.673*10-11 Nm2/kg2.
- And most important thing is that, the Newton’s law of gravitation is applied to all objects irrespective of the masses of the objects and the distance between the objects. Hence, Newton’s law of gravitation is called as universal law.
- The SI unit of Gravitational constant G is Nm2/kg2
- And the dimensions of G are [ L3 M-1 T-2].
- And from the statement of Newton’s law of gravitation we observe that, as the distance between the objects increases the gravitational force decreases and if the masses of the objects increases then gravitational force increases.
Example:
Let us suppose A and B are the two objects which are separated by the distance 5m.
Let object A is having 10kg mass and object B is having 15kg mass. What is the gravitational force of attraction between the objects A and B here?
Solution:
Given that,
M1 = 10 kg
M2 = 15 kg
r = 5m
F= ?
We know that,
The gravitational force of attraction between two objects is given by,
F = GM1*M2/r2
F = 6.673*10-11*10*15/5*5
F = 6.673*6*10-11
F = 40.038*10-11 N
Thus, the gravitational force of attraction between given objects A and B is 40.038*10-11 N.
Note:
- The raindrops are falling down and not falling in upward direction. The raindrops are falling down only because of the gravitational force of attraction between the raindrops and the earth.
- And also, every object of any mass thrown in the upward direction falls down after sometime only due to the gravitational force of attraction between the object and the earth.
- The gravitational force acting on each body is different and depends on the mass of the body and distance of separation between them. But the acceleration due to gravity g acting on each body is same and it has constant value and its value on the earths surface is g = 9.8 m/s2.