- Books Name
- Science Made Easy Science Book
- Science Made Easy
- CBSE Class 9
→ The ratio of the density of a substance to that of the density of water is called relative density.
• Relative density = Density of a substance/Density of water
→ It has no unit as it is a ratio.
Kepler’s laws of planetary motion
Kepler observed that different planets take different time to complete one revolution around the sun. From s this observation of planetary motion he deduced that square of time period is proportional to the cube ob its distance from the sun.
Kepler’s First Law
Kepler’s first law of planetary motion states that planets move around the sun in such a way that sun always remains at one of its focus.
Kepler’s second law
According to second law the line joining planet to the sun sweeps out equal area in equal time interval, as the planet revolve around the sun in a elliptical orbit.
Kepler's Third Law
It states that square of time period is proportional to the cube of its semi major axis.