Question

As shown in figure, a planet revolves in elliptical orbit around the sun. Where is KE of the planet maximum?

• A. At $P_4$
• B. At $P_1$
• C. At $P_2$
• D. At $P_3$

Answer 1

Answer: (A)

At $P_4$

Answer 2

By the Iaw of conservation of anguiar momentum, we have
\hspace30mm J = I \omega = constant
where, I is moment of inertia and co is angular velocity.
Also, \hspace15mm I = MR^2 and $\omega = \frac{v}{R}$
\therefore \hspace30mm v \propto \frac{1}{R}
At $P_4$ the value of R is minimum, hence the velocity is

maximum or kinetic energy will be maximum.