## Kepler’s law

Kepler’s law – 1) First low (law of orbital)

Every planet revolves around the sum in an elliptical orbit. The sum is situated at one focus of the ellipse.

2) Second law (law of area)

The radius vector drawn from the sun to the planet sweeps out equal area in equal intervals of time i.e. the real velocity of the planet around the sun is constant i.e areal velocity dA/dt=a constant, for a planet.

3) Third law (law of period)

The square of the time period of revolution of a planate around the sun is directly proportional to the cube of semi- major axis of the elliptical orbit. It means, larger is the distance of planate from the sun, greater will be its time period of revolution. That is why the time period of revolution of nearest planet mercury is 88 days (i.e. least) and that of farthest Pluto is 248 years (maximum).