Drop an apple, use a stopwatch to see the landing time, and use the law of free fall to calculate the height of the building s = 0.5 * a * t 2.

A is the acceleration, the magnitude is 9.8 S, and it is the height of the building.

Since the human reaction speed is about 0. 1 sec, the stopwatch time should be subtracted from 0. 1 sec.

There is still a mistake. Everyone's reaction speed is different. If you want to be accurate, you can take a test. Let others take a ruler. You put your index finger and middle finger on both sides of the ruler and let the person holding the ruler let go at will. Look at the difference between your initial position and your final position. Calculate your reaction time t with S = 0.5 * A * T 2, and then bring it into the previous formula. Hope to adopt