If an object is moving then it is, by virtue of that motion,
capable of doing work. This energy of motion is called "kinetic
energy." The kinetic energy of an object is equal to 1/2
of its mass times its velocity (or speed) squared (KE=1/2M-V2).
Tony demonstrates the conversion of one form of energy into another. As Tony pulls back on the string he exerts a force over a distance and thus does work on the bow. He gives the bow elastic potential energy. This energy is released when Tony lets go of the bow string. Then, the bow string exerts a force on the arrow as it pushes it over a distance. It does work on the arrow, giving it energy kinetic energy of motion.