1. The problem statement, all variables and given/known data The space shuttle makes 1 revolution around the Earth in 1.5 hours when it is in an orbit 200 km above the Earth’s surface. The radius of the Earth Re is 6.5 × 10^6m. If the shuttle moves to a new orbit such that it makes 1 revolution per day (24 hours), what is the radius of the new orbit? (1) 6.2Re (2) 12Re (3) 24.8Re (4) 16Re (5) 0.38Re 2. Relevant equations Force_centripetal=Force_gravity v=(2piR)/T T=period 3. The attempt at a solution My professor said: "Yes, the centripetal force is provided by gravity. The tangential velocity v=2piR/T where T is the period. Thus show that T is proportional to R^2 and solve. For orbit 2, R_2=R_1sqrt(T_2/T_1)" ...but I still can't understand what he's talking about. What does he mean that period T is proprtional to r^2? And what does any of this have to do with balancing the centripetal force with the force of gravity? Thank you. This forum is the best.