Q 11-07-032NEETJEE MainMedium
A planet moves in an elliptical orbit around the Sun. Its distances from the Sun at perihelion and aphelion are $r_1$ and $r_2$. The ratio of its speeds at perihelion and aphelion is
Answer: (D) $\dfrac{r_2}{r_1}$
Angular momentum is conserved. At perihelion and aphelion the velocity is perpendicular to the radius, so $mv_1r_1 = mv_2r_2$:
$$\frac{v_1}{v_2} = \frac{r_2}{r_1}$$
The planet moves fastest when closest to the Sun.
Solution by Sreeraj P, M.Sc Physics