The momentum of an object is given by p = mv, where p = momentum, m = mass of object and v = velocity.The kinetic energy of an object is given by KE = 1/2 * mv2 where KE is the kinetic energy. Therefore to convert from momentum to kinetic energy, one must multiply the momentum of the object by 0.5v, as KE can also be written as KE = 0.5 (mv)v (= 0.5p*v).