posted by Harold .
A rock is dropped from a hotel and strikes the ground with a particular speed. In order, to double the speed at impact, you would have to drop the rock from the hotel at?
I say impossible to determine
Yoy would have to from the rock from four times the height to get twice the velocity at impact (neglecting air friction). That is because kinetic energy in proportional to V^2. You'd need four times the kinetic energy, and that comes from four times the height (and potential energy)