Physics
posted by Eli .
A stone is dropped into a deep well and is heard to hit the water 2.95 s after being dropped. Determine the depth of the well.

Solve this equation for the depth, H:
T = 2.95s = (time to fall) + (time for sound to arrive)
= sqrt(2H/g) + H/(340 m/s)
Convert it to a quadratic equation for H and solve for the positive root. 
Water flows (velocity initial=0) over a dam at the rate of 660 kg/s and falls vertically 81 m before striking the turbine blades. Calculate the rate at which mechanical energy is transfered to the turbine blades, assuming 55% efficiency.

s=ut 1/2 at0…5
s=o(2.95) 1/2(9.8)(2.95)0…5
s=0 42.64
s=42.64 m (approx.)
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