physic
posted by ozer on .
Planet A and planet B are in circular orbits around a distant star. Planet A is 4.5 times farther from the star than is planet B.
What is the ratio of their speeds vA/vB?

mv²/R=GmM/R ²
v= sqrt (GM/R)
v₁/v₂= sqrt(R₂/R₁) =sqrt(1/4.5)=0.47