Home Forums Hunting & Shooting Ask The Gunwriters Foot Pound Energy

E = m c^2 is NOT the correct formula... .c = speed of light, not just any velocity



The correct formula for KINETIC energy is

KE = 0.5 * (mass * velocity * velocity)

mass = grains / (7000 * 32.2) [7000 grains per pound; divide by 32.2 to convert mass into a weight, yes they're different]

velocity = in fps

Units work out to be [grains * lb/grains *sec^2/ft] * ft^2/sec^2
grains cancel out; sec cancel out; one ft gets cancelled .... leaving ft-lbs


Example:

140 grain bullet @ 3000 fps

KE = 0.5 * (140/(7000 * 32.2)) * (3000 * 3000) = 2795 ft-lbs of energy