Physics homework without SHOUTING
Airplanes are noisy things. For example, if you stand really close to a runway, a military jet can produce a sound intensity of about at a distance of 30 m from the plane (this is beyond painful noise). You live near a military airport and want to work on physics with your friend. Since you don't want to shout, you decide to find a spot far enough away from the airport that the airplane noise is below the threshold of conversation . How far do you need to go from the airport in kilometers to accomplish this?
The answer is 300.
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1 solution
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The intensity of sound falls off as 1 / d i s t a n c e 2 . Hence we have I 1 r 1 2 = I 2 r 2 2 . We can solve this for r 2 = 3 0 0 k m .