NEWTONS'S LAW OF GRAVITATION. all bodies in this universe attract each other with a force that is directly proportioned to the product of their masses and inversely proportioned to the distance of their square
moon moves around the earth due a centripetal force supplied by gravitational force between earth and moon
according to keplers's second law,the line joining plaet and the sun sweeps out eqaul area in equal time
according to keplers's thirds law,cube of mean distance r of the plaet from the su is proportional to the sqaure of its orbit
according to ewtons law of gravitation
Now, Law of Gravitation also states that force of attraction by which an object attracts other object is inversely proportional to the square of distance between them.Now from equation (i) and (ii) we get
here G is a constant and called universal consant of gravitation,its value is 6.673*10raise to the power-11 Nm²kg-²
acceralation due to gravity is greator at poles than the eqauter
The earth attracts objects towards it due to gravitational force. When an object falls towards the earth due to the earth’s gravitational force it is called free fall.
When an object falls towards the earth there is a change in its acceleration due to the gravitational force of the earth. So this acceleration is called acceleration due to gravity.
The acceleration due to gravity is denoted by g.
The unit of g is same as the unit of acceleration ms -2 From the second law of motion, force is the product of mass and acceleration. F = ma For free fall, force is the product of mass and acceleration due to gravity. F = mg mg = G M x m/d2 g = G m/d2
where M is the mass of the earth and d is the distance between the object and the earth.
For objects near or on the surface of the earth d is equal to the radius of the earth R mg = G M x m/ R2 or g = G M/ R2The value of g is 9.8 ms -2
The mass of a body is the measure of its inertia. If the mass of a body is more its inertia is more. The mass of a body is constant and does not change from place to place. The SI unit of mass is kg.
The weight of an object on the earth is the force with which the earth attracts the object and the weight of an object on the moon is the force with which the moon attracts the object.
The mass of the moon is less than the mass of the earth. So the moon exerts lesser force on the objects than the earth.
The weight of an object on the moon is one sixth (1/6th) of its weight on the earth