Sir Dudley the Dextrous is loading cannons on top of the castle's tallest towers in preparation for an expected attack. He slips, and a cannonball of mass 14.0 kg 14.0 kg rolls to the edge of the tower, which has a perfectly horizontal surface, and falls to the ground below. It takes the cannonball 3.15 s 3.15 s to fall to the ground, and air resistance is negligible. How much work is done by gravity on the falling cannonball?