Try this with your friends. Hold a dollar bill so that the midpoint hangs between a friend's fingers and challenge him to catch it by snapping his fingers shut when you release it. He won't be able to catch it! Explanation: From d = ½ gt2, the bill will fall a distance of 8 centimeters (half the length of the bill) in a time of 1/8 second, but the time required for the necessary impulses to travel from his eye to his brain to his fingers is at least 1/7 second.