Dynamics Started work on gravity in 1666 Knew of work of Galileo through Descartes Body in constant motion didn't need force to keep moving Freely falling body increases speed at constant rate. Tradition of apple falling used to explain why moon doesn't fall into earth.
Cannonball has motion down and forward force of gravity is a constant.
If constant force produces constant accleration, than changing force would produce a changing accleration. Let all mankind rejoice that an ornament to humanity of this kind, and so great an ornament, has existed.