Two satellites A and B go round a planet P in circular orbits having radii 4R and R respectively. If the speed of the satellite A is 3V, the speed of the satellite B will be : 

6 V

Orbital velocity of satellite :

\(v = \sqrt{\frac{GM}{r}}\)

\(\Rightarrow v \propto \frac{1}{\sqrt{r}}\)

\(\Rightarrow \frac{v_B}{v_A} = \sqrt{\frac{r_A}{r_B}}\)

\(\Rightarrow \frac{v_B}{3 V} = \sqrt{\frac{4R}{R}}\)

\(\Rightarrow v_B = 6 V\)