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professordad
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Homework Statement
A pebble is dropped into a deep well, and 3.0 seconds later the sound of a splash is heard as the pebble reaches the bottom of the well. The speed of sound in air is about 340 m/s.
(a) How long does it take for the pebble to hit the water?
(b) How long does it take for the sound to reach the observer?
(c) What is the depth of the well?
From College Physics by Serway and Faughn
Homework Equations
[itex]v = v_0 + at[/itex]
[itex]x = v_0t + \frac{1}{2}at^2[/itex]
[itex]v^2 = v_0^2 + 2ax[/itex]
The Attempt at a Solution
(a) So in this problem we know the acceleration (which is the gravitational constant) and we also know [itex]v_0[/itex] which is 0 because it starts out as 0 m/s. But in all three equations, there are 4 variables, and knowing 2 variables is not enough.
Then I tried plugging in and obtaining a system. So I got
[itex]-19.6x = v^2[/itex]
[itex]v = -9.8t[/itex]
But this doesn't help much, and if you add a 3rd equation its going to be the same thing (the three equations are related). So I don't know how to proceed :(
Also for (b) and (c) I think you need (a) to solve them.
BTW I'm out of school, so this problem doesn't count for a grade or anything :)