c903,
Actually, KE is the force derived from the weight of the arrow at a given impact velocity. Where in the equation below velocity is actually the impact velocity of the arrow.

KE = (1/2)*mass*velocity*velocity, in (ft*lbs)

Kinetic energy is the work done on an object over a given distance, so in physics terms:

work = Force * distance = KE

As expressed above, KE = (1/2)*mass*velocity*velocity.

In order to make the above equations come out in the units of ft*lbs, which is what we bow hunters like to know, you have to work out the above equations in SI notiation (kg for mass & m/s for velocity) this will give you an aswer in Joules which can then be converted to ft*lbs. Several archery manuals will have a unit conversion built into the equation which allows you to use a modified version of the KE equation above and you can use fps and grains instead of SI units.

Hope this helps...

Redneck