posted by raj on .
to find the depth of the water surface in a well, a person drops a stone from the top of the well and simultaneously starts a stopwatch. The watch is stopped when the splash is heard, giving a reading of 3.65 s. The speed of sound is 340 m/s. Find the depth of the water surface below the top of the well. Take the person's reaction time for stoppping the watch to be 0.250 s.
stone time (T) plus splash time (t) equals watch time minus reaction time
T + t = 3.65 - .25 __ t = 3.4 - T
d = .5 * g * T^2 __ g = 9.8 m/s^2
also, d = 340 * t __ d = 340(3.4 - T)
4.9 T^2 = 1156 - 340 T
4.9 T^2 + 340 T - 1156 = 0
use quadratic formula to find T, then plug in to find the depth