A hunting arrow with a properly sharpened head and weighing in the neighborhood of 0.07 to 0.10 lb., with a kinetic energy of 50 to 60 ft. lb., has very little shocking power but amazing penetration. It will completely penetrate almost any large game animal. Since, for a given resisting force, depth of penetration varies directly as the kinetic energy of the arrow, it is better to use a heavy rather than a light shaft with a given bow. The reason is, as was shown previously, that the heavier arrow takes more of the available energy from the bow than does a light one. Equations (1) and (2) enable one to compute readily the efficiency of a particular bow of known virtual mass with arrows of various masses. From this information relative penetrations can be estimated.