College Physics
posted by Marcus .
A rock is dropped from a sea cliff and the sound of it striking the ocean is heard 6.4 s later. If the speed of sound is 340 m/s, how high is the cliff?

The time of 6.4 s is the sum of the time required for the rock to hit the sea, sqrt (2H/g), and the time for the sound to get back, (H/V).
H = cliff height
V = speed of sound
g = acceleration of gravity
Solve this equation for H:
6.4 = H/340 + sqrt(H/4.9)
That can be turned into a quadratic equation. Only one root will be positive. 
172.35

356.8