Discuss the interaction which occurs when a bullet or cannon shell is fired from a weapon. Compare the forces that exist between the cannon and the cannonball. Elicit from Newton's third law that the forces should be equal and opposite. Why does the cannonball move faster than the cannon recoils if the forces are the same? Determine from the formula force=mass x acceleration, that it is the acceleration which propels the object. Discuss the relationship between acceleration, force and mass.