Question
Mention Kepler's law.
✓
Answer
Kepler's law :
(i) Every planet revolves around the sun in an elliptical orbit and the sun is at one focus of the orbit.
(ii) The line joining any planet to the sun coasses the same area in equal time intervals i.e., regional velocity of the planet $\left(\frac{d A}{d t}\right)$ remains fixed.
(iii) The square of the period of revolution of a planet is proportional to the third power of the average distance of the planet from the sun. That is,
$\begin{aligned}
T^2 & \propto r^3 \\
T & \propto r^{3 / 2}
\end{aligned}$
$T=K r^{3 / 2} \text { where } K \text { is constant. }$
The law of areas can be considered as a conclusion of angular momentum conservation which is valid for all central forces. The central force acting on a planet acts along the vector joining the central sun and the planet.
(i) Every planet revolves around the sun in an elliptical orbit and the sun is at one focus of the orbit.
(ii) The line joining any planet to the sun coasses the same area in equal time intervals i.e., regional velocity of the planet $\left(\frac{d A}{d t}\right)$ remains fixed.
(iii) The square of the period of revolution of a planet is proportional to the third power of the average distance of the planet from the sun. That is,
$\begin{aligned}
T^2 & \propto r^3 \\
T & \propto r^{3 / 2}
\end{aligned}$
$T=K r^{3 / 2} \text { where } K \text { is constant. }$
The law of areas can be considered as a conclusion of angular momentum conservation which is valid for all central forces. The central force acting on a planet acts along the vector joining the central sun and the planet.
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