7.0 Kepler's law of planetary motion

  Gravitation

Johannes Kepler formulated three laws between 1609 to 1619 which are popularly known as Kepler's law of planetary motion.

The three laws are,

1. Kepler's first law (law of orbits): Each planet moves in an elliptical orbit with the sun at one foci of the ellipse.

2. Kepler's second law (law of areas): The radius vector drawn from the sun to the planet sweeps out equal areas in equal to an interval of time.

3. Kepler's third law (law of periods): The square of the time period of revolution of a planet around the sun is directly proportional to the cube of the semi-major axis of the elliptical orbit.