"Given a planet has mass M and radius R, find the speed it would have to be launched at. Compare this to the speed required to put the object in the circular orbit." I understand the first half where Ep=Ek i.e: GMm/r = 1/2 mv2 rearrange to find v how ever, i'm unsure of what exactly the 'orbit velocity' is. is the the value of v in centripetal force, F = mv2/r is this the same as the speed needed to launch it in to orbit or what? i am rather stumped here..