posted by andrea .
A meterstick is held vertically above your hand, with the lower end between your thumb and first finger. On seeing the meter stick released, you grab it with those two fingers. You can calculate your reaction time from the distance the meterstick falls, read directly from the point where your fingers grabbed it.
Derive a relationship for your reaction time in terms of this measured distance d.
d = (g/2)t^2
t = sqrt(2d/g)