Question

Two satellites $P$ and $Q$ are revolving around earth in different circular orbits. The velocity of $P$ is twice the velocity of $Q$. If the height of $P$ from earths surface is 1600 km. The radius of orbit of $Q$ is $($ Radius of earth $R=6400$ km $)$.

• A. $1600km$
• B. $20000km$
• C. $32000km$
• D. $40000km$

Answer 1

Answer: (C)

$32000km$

Orbital velocity is related to the distance from Earth's centre as
$\frac{v_2}{v_1}=\sqrt{\frac{r_1}{r_2}}$
$\Rightarrow \frac{r_1}{r_2}=\frac{v_2^2}{v_1^2}$
$\Rightarrow r_1=r_2\times \frac{v_2^2}{v_1^2}=(6400+1600)\times \frac{2^2}{1^2}=8000\times 4=32000$ $km$