Jon is standing on a bridge over a creek. He releases a stone 20 feet from the water. How long will it take the stone to hit the water?

The distance covered by a free-falling object in 'T' seconds after it's dropped is

D = (1/2) x (gravity acceleration) x (T²)

Gravity acceleration on Earth is 9.8 m/s². or 32.2 feet/sec².

20-ft = (1/2) (16.1) (T²)

20 = 8.05 T²

T = √ (20/8.05) = 1.576 seconds.