Drop Timer

Drop a small object and start the stopwatch the moment it leaves your hand, then stop it the instant it lands. The tool converts that time into a distance. A stone down a well, a pebble off a bridge, or a coin down a stairwell all work. Drop it several times, save each one, and use the average — that cancels most of your timing error.

Ignoring air, an object dropped on Earth falls about 4.9 m (16 ft) in one second, 19.6 m (64 ft) in two, and 44.1 m (145 ft) in three. The distance goes as the square of the time, so doubling the fall time quadruples the drop.

The first is the textbook answer, d = ½gt², which assumes no air. The second accounts for drag: everything falling through air eventually reaches a terminal velocity and stops speeding up. Under about two seconds the two barely differ, but beyond that the vacuum figure overstates the drop — after five seconds a real pebble has fallen noticeably less than the 123 m the formula predicts.

Your reaction time is the limit. A tenth of a second either way is normal, and because distance grows with the square of time that error matters more the longer the fall. The tool shows the resulting ± range under the headline number so you can see what your timing is actually worth. Averaging several drops is the simplest way to tighten it.

Yes, if the drop is deep. Sound takes about one second to travel 343 m back up, so on a very deep shaft the noise reaches you measurably late and makes the fall look longer than it was. For anything under about 30 m the delay is under a tenth of a second and you can ignore it.

Not in a vacuum — gravity accelerates everything equally, which is why a feather and a hammer land together on the Moon. In air, mass matters indirectly: a heavier object of the same size has a higher terminal velocity, so it keeps accelerating for longer. That is why the object picker changes the second number but never the first.