The Work-Energy theorem in mechanics relates the kinetic energy of a body at two positions to the work done on the body during its motion from some position 1 to a second position 2 along some specified path.

        K2 = K1 + W12

where

        K2 = 0.5*m*v2^2 ,
        K1 = 0.5*m*v1^2  and
          W12 = net work done by all forces on the body from position 1 to position 2 along the specified path