Calculating Distance From a Falling Stone

Interception

Ok, so I watched a horror movie recently and they did the whole drop a rock down a cavern and see how long it took to hit the bottom. Couldn't you find the approximate distance through this? Not just a guess like "Oh that took a little bit so it's waaaay down there".

If two objects accelerate at the same rate due to the pull of gravity, if you could calculate the speed, wouldn't it pretty much be used as an assumed constant? Then if you knew the speed, all you would have to do is divide that by the time it took to hit the bottom using Speed= Distance x Time. But then again, if you were at a higher point and dropped it, wouldn't it have more space to accerlate and throw off your results? I'm just looking for an estimate, it doesn't have to be exact.

Creator

The formula is simple:
assuming zero initial velocity, the distance, s, fallen is:
s = (1/2)(-gt^2)