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# Urgent! Physics Help!

1. A fireworks shell explodes H=110 m above the ground, creating colorful sparks. How much greater is the sound level of the explosion for a person at a point directly below the explosion than for a person a horizontal distance of L=190 m away?

### 2 Answers by Expert Tutors

Philip P. | Effective and Affordable Math TutorEffective and Affordable Math Tutor
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A fireworks shell explodes H=110 m above the ground, creating colorful sparks. How much greater is the sound level of the explosion for a person at a point directly below the explosion than for a person a horizontal distance of L=190 m away?

The intensity of the sound waves drops off as 1/r2 where r is the distance from the point where the sound is made.  One observer is at a distance r1=110 m; the other is at a distance of r22 = 1102 + 1902 from the explosion.

Take the ratio of observer 1's sound level to observer 2's:

(1/r12) / (1/r22) = r22/r12

Plug in the values of r1 and r2 to solve.

I got 3.98 dB, but Mastering Chemistry keeps counting it wrong. It would just be 48200/12100 which equals 3.98, right?
3.98 is right but it's not in decibels.  To convert the intensity to decibels:

I = (10)log10(3.98) = 6
Thank you so much! I understand it now (:
Robert A. | Certified Teacher and Engineer - Tutoring Physics, Maths, and SciencesCertified Teacher and Engineer - Tutorin...
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I wonder why you posted the same question twice.   Please post once, it saves duplicate efforts on our part.

Also - I am curious, you said you were using Mastering Chemistry.  Is this a problem in a chem class?
I did the most study of this in an EE class on e/m fields and waves, chem seems a strange place for this.
There are a couple extra tidbits in the answer to the other post you might find interesting.