silentassassin wrote:
Using your analogy a 40 lbs bow shotting a 40 lb arrow (that it can't even budge) would have more kinetic energy than the same bow would shooting a lighter projectile than it could a 400 grain aroow that it could propel at 180 fps.
Actually 40 lbs of force acting on a 40 lb arrow will accelerate it horizontally at 32.16 ft/sec/sec and if by some miracle you could construct a bow that was capable of handeling both a 400 grain and a 40 lb arrow, all things being equal the 40 pound arrow would be propelled more efficiently than the 400 grain arrow. It would of course be moving much slower but it would carry more KE. Now insted of shooting the arrow horizontally you turned the bow vertical (this is what you are attempting to set up) you would still be accelerating the arrow at 32.16 ft/sec/sec but because gravity would oppose with an equal and opposite acceleration the net force on the arrow would be 0 so you are now doing what I said in a prior post. You have so exagerated the system that you are inadvertanly changing other factors and aren't compairing apples to apples. Your distorted scenario actually compares a 40 lb bow acting on a 400 grain arrow vs a 0 pound bow acting on a 40 pound arrow. When you stay in the realm of realistic conditions and only change the mass of the arrow, the more mass the more KE and the less mass the less KE. There is no getting around it!