What is the speed of Satellite B?

Question

Two satellites are in circular orbits around Earth. Satellite A has speed vA. Satellite B has an orbital radius nine times that of satellite A. What is the speed of Satellite B?

A. vA.9

B. vA/3

C. 3vA

D. 9vA

Answer 1

Recall from centripetal force in circular motion,

v_A = √(GM/r_A)

v_{B =} √[GM/(9r_A)] = (1/3) √(GM/r_A) = v_A / 3