Find the Height of a Cliff with Sound Homework Help - Expert Guidance"

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To find the height of the cliff, the problem involves calculating the time it takes for a stone to fall and the time for the sound of the splash to travel back up, totaling 3.5 seconds. The equations d = 1/2 at^2 for the stone's fall and v_sound = d/t for the sound's return are used to solve for distance. The approach requires combining the time for both events to equal 3.5 seconds and solving for the height. Additionally, a separate question about calculating the power output of a speaker based on a dB meter reading at a concert is also posed. The discussion seeks assistance in applying these concepts to solve both problems effectively.
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Ok I need guidance on how to approach this problem. The problem is as follows: A stone is dropped from the top of a cliff. The splash it makes when striking the water below is heard 3.5s later. How high is the cliff?
 
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Does anyone know the answer to this problem?
 
the time is of course the time for it to fall plus the time for the sound to come back up. So therefore use d=\frac{1}{2}at^2 and v_{sound}=\frac{d}{t} then you solve both for time and add them together to produce 3.5 and hence solve for d.
 
ok I had those equations I just didn't think what to do. CAn you help me with this problem also: At a rock concert, a dB meter registered 130 dB when placed 2.8m in front of a loudspeaker on the stage. What is the power output of the speaker, assuming uniform spherical spreading of the sound and neglecting absorption in air?

Someone help me please?
 
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