If you drop a stone into a mine shaft 128.0 m deep.....

Question

i think it looks simple..but i do not know wat to do or where to start....

If you drop a stone into a mine shaft 128.0 m deep, how soon after you drop the stone do you hear it hit the bottom of the shaft?

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Answer 1

D=(1/2)(a)(t^2)

so

128m = (1/2)(9.8m/s/s)(t^2)

solving for t we get 5.1seconds

if we take into account the speed of sound in air then it would be 5.5 seconds