Ouch, I got myself stumped. Say we are given the energy of a system (in this case let's consider it a hypothetical gravity wave). I have the energy of the wave that it has, derived from the change in momentum of the object it interacted with. I want to determine the force of gravity between the two objects to henceforth calculate the mass of the object emitting the wave (assume distance is known in this case as well). I suspect maybe it is a simple matter just going back to the change in momentum, but am not certain if there is another way given the energy of the wave. Any insights?