CHARACTERTICS OF GRAVITATIONAL FORCE

i)                 It is always attractive

ii)             It is independent of the medium between the bodies. In contrast electric and magnetic forces are medium dependent.

iii)          It holds good over a wide range of distances ranging from interatomic distance to intergalactic distance. Its range is infinitive.

iv)           Gravitational force is conservative.

v)              The presence of solar system and planets revolve round the sun due to the presence of gravitational force.

vi)           The presence of atmosphere on the earth is due to the gravitational force.

vii)       The gravitational force of the earth keeps us firmly on the surface of the earth.

viii)    Tides in seas and oceans are due to the gravitational force of the sun and moon.

PROPERTIES OF G

1.   The value of G is independent of the nature and chemical composition of the masses of the bodies, and the medium in which the bodies are occurred.

2.   The value of G is unaffected by temperature and pressure.

VALUE OF G

A scientist henry Cavendish determined the value of G experimentally by using extra sensitive apparatus, The value of G is 6.67×10ˉˡNm²kgˉ².

GRAVITATIONAL CONSTANT G

If m1=m2=1 unit and r=1 unit, then, equation(7.1) reduces to G=F

Universal gravitational constant G is numerically equal to the force of attraction between two unit point masses separated by unit distance. Its value is 6.673×10-ˡˡ Nm²kg² in SI and 6.673×10-8 dyne cm²/g² in CGS system. Its dimensional formulae is mˉˡl³tˉ²

The value of G is same everywhere between all bodies in the universe. All our observation confirm this. Newton’s law of universal gravitation is applicable to bodies as small as electronic and atoms and as big as galaxies and cluster of galaxies.