Public School, Deer Creek Minnesota, 1918 LakesnWoods.com Postcard and Postcard Image Collection - click image to enlarge Aerial view, Deer Creek Minnesota, 1972
Whenever work is done upon an object by an external force, there will be a change in the total mechanical energy of the object. If only internal forces are doing work (no work done by external forces), there is no change in total mechanical energy; the total mechanical energy is said to be conserved.
If no forces are acting on a moving object, it will eventually come to rest.. It is not true. If no forces act on a moving object, it will continue at constant velocity. It takes an unbalanced force to stop an object in motion.