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.

Answer 1

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

Answer 2

3.57