[Mike Schreiber]

Originally Posted by Ether

In most catapults and kickers, a large portion of the spring energy is not imparted as kinetic energy to the ball. Thus this equation will give a substantially over-optimistic estimate of ball speed if "x" is the total amount the tubing is stretched (including pre-tensioning stretching).

You can increase the available spring energy by adding more strands or tubing and/or pre-tensioning the spring (or surgical tubing) with the launcher (or kicker) against the hard stop in the "fired" position.

That is true for catapults, but I was under the impression that a linear launcher (like I imagined they were using if they were asking about angle from an arm) would be more efficient at energy transfer. With the exception of friction what would prevent it from imparting energy? Deformation of the ball?