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# CBSE Class 9 Answered

what is Newton's contribution on gravitation?
Asked by munendramishra478 | 12 Jul, 2022, 08:42: PM Expert Answer
From the observation of motion of moon and other celestial objects , Newton was able to arrive universal law of gravitation .
Newton's universal law of gravitation explained the terrastrial gravitation and Kepler's law of motion of planets.
From the observation of falling objects towards earth , Newton reasoned there is a force of attraction between objects and earth
that is known as gravitational force or gravity.

Newton thought that the moon revolving in an orbit of radius Rm was due to centripetal acceleration am
experienced by moon because of earth's gravity.

hence he worked out as

am = ( v2 / Rm ) = 4 π2 Rm2 / T2 ...........................(1)

where v is speed of moon, Rm is distance between centre of moon and centre of earth and T is period of revolution

In above expression speed of moon v is substituted as  v = ( 2πRm ) / T

hence , we get ,  T2 / Rm3 = 4π2 /v2 = constant

Above expression proves Kepler's law of periods

Newton calculated the centripetal acceleration experienced by moon using eqn.(1) .

By comparing this acceleration with acceleration due to gravity on earth , he came to the conclusion that
this acceleration is inversely proportional to square of distance between centre of moon and centre of earth.

These observations led Newton to propose the following Universal Law of Gravitation :

" Every body in the universe attracts every other body with a force which is directly proportional
to the product of their masses and inversely proportional to the square of the distance between them "

Mathematically, Newton’s gravitation law states  that  the force F on a point mass m2 due to
another point mass m1 has the magnitude where d is distance between m1 and m2

Universal Law of Gravitation is the contribution of Newton in Gravitation

Answered by Thiyagarajan K | 13 Jul, 2022, 12:37: AM

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