conservation of ENERGY states that Energy can neither be created nor be DESTROYED but can be transferred from one form to another.In the case of free falling body P.E converts into K.ECase 1:Consider an object of mass(m) which is made to fall freely from a certain HEIGHT(h).At the starting point A, P.E is maximum & K.E is minimum because the velocity of an object become zero.Total energy(T.E) = P.E + K.E                       T.E = P.E + 0                       T.E = mghCase 2:At point B(mid-point in air), the velocity of an object will increase & height of the object will decrease hence the P.E will be CONVERTED into K.E.Total energy(T.E) = P.E + K.E                      T.E  = mgh + 1/2mv^2(square)Case 3:At point C(slightly above the ground in air), an object is just above the ground & body will have a certain velocity & acquire a K.E.Total energy(T.E) = P.E + K.E                        T.E = 0 + K.E                        T.E = 1/2MV^2(square)CONCLUSION:The sum of energies is same at all points.Potential energy(P.E) + K.E = Constant      mgh + 1/2mv^2(square) = Constant = Mechanical energy(M.E)