Question

The answer is Vb = Va^2. But I want to know why. I'm guessing it's because of Keplers Third Law - Va is the orbital speed of a satellite at a distance x from the centre of the Earth. If the satellite is at a distance 2x from the centre of the Earth and with the speed of Vb, which of the following statements is correct?

Answer 1

When I solve this I get

Va^2 = Gm/r

and Vb^2 = Gm/2r

Equating them you get 2(Vb^2) = Va^2

And the answer was Vb = Va^2 ?????

Answer 2

What answer?