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Sound Intensity and Distance

A loudspeaker is placed between 2 observers who are 120m apart, along the line connecting them. If one observer records a sound level of 60.0 dB and the other records a sound level of 90 dB, how far is the speaker from each observer? Hint: use the equation which relates to the difference between the decibel levels to the distance from the source.
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Answers:
a) 3.7, 116.3
b) 4.3, 115.7
c) 6.2, 113.8
d) 8.6, 111.4
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A body oscillates with simple harmonic motion along the x-axis. Its displacement varies with time according to the equation x=5sin(3.14t + 3.14/3). pi=3.14. The velocity (in m/s) of the body at t=1 second is:
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a) +8
b) -8
c) -14
d) +14
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OTA: please take this problem only if you can show step by step problem solving and equations used. Also, very important, show why the final answer is a positive or negative sign. Thank you.

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