Originally Posted By: K
Here the spring is much more efficient than the horse because it doesn't consume energy when its not doing any work. You can leave it for years applying the same force and never have to recharge it.


Are you not overlooking the fact that the spring behaves as an elastic solid only for a finite period of time, albeit a long time? Eventually it will behave as a plastic solid. Its molecules will re-arrange themselves, with production and loss of heat, so over the long term the energy in the spring will be lost. Perhaps you would need to be holding one end of the spring to appreciate the energy exchange involved.

There never was nothing.