1. The problem statement, all variables and given/known data I am trying to calculate the exit velocity of an arrow from a bow. I am an archer and this is for my own personal knowledge so I need to keep the units meaningful in lbs, sec, mph, inches. The end velocity must me in mph. 2. Relevant equations The equation that I have found that best applies is: v = (eFx/m)^-2 v = The exit velocity. e = The efficiency (all force applied in the same direction). We can assume it will be 70% for most medieval bows. F= The force to draw the bow fully, commonly known as draw-weight. m= Mass of the arrow. x= This is the distance that the string will travel from its rest position to its fully drawn position. 3. The attempt at a solution e= 70 % f = 100 lbs m= .5 lbs x = 30 inches v= (.7x100 lbx30 inch /.5 inch) ^-2 3000 inch lbs / .5 inch .7 x6000 lbs 4200 lbs ^-2 5.66 lbs sq I don't understand what 5.66 lbs sq means.