Question

Mr. Physics drops a rock down a 250-meter deep well. Upon impact with the bottom burst of sound is produced with a frequency of 250 Hz. How much time after he drops he hear it hit the bottom of the well. (Use GUESS method.) Answer 7.87 seconds the rock does

Answer 1

Solution) This problem is based on kinematics

We have distance

d = ut + (1/2)at^2

Here we need to find time during rock going down and up

as shown

This problem is based on kinematics we have distance d = ut + (1/2) at^2 Here we need to find time during rock going down and up \r\n d = 250m f = 250 Hz time T = ? we know velocity of sound, v = 343 m/s when dropped, u = 0 m/s d = ut + 1/2 gt^2 250 = (0) (t_1) + 1/2 (908) t^2_1 doublerightarrow 4.9 t^2_1 = 250 t^2_1 = 250/4.9 doublerightarrow t_1 = squareroot 250/4.9 = 7.1428 t_1 = 7.143 s (time during going down the well) we have, d = v t_2 250 = (343) t_2 t_2 = 250/343 = 0.729 s (time during going back up the well) therefore time, T = t_1 + t_2 T = 7.143 + 0.729 T = 7.872 s T = 7.87 s