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A siren creates a sound level of `60 H_(Z)` at a location `500 m` from the speaker. The siren is powered by a batter that delivers a total energy of `1.0 kJ`. Assuming that the efficiency of siren is `30%` , determine the total time the siren can sound. |
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Answer» Sound level (in `dB`) `L = 10 log_(10) ((I)/(I_(0)))` where, `I_(0) = 10^(-12) W//m^(2)` `L = 60 dB` Hence, `I = (10^(6)) I_(0) = 10^(-6) W//m^(2)` Intensity, `I = (Power)/(Area) = (P)/(4 pi r^(2))` rArr `P = I (4 pi r^(2))` `P = (10^(-6))(4 pi)(500)^(2) = 3.14 W` :. Time, `t = ((10 xx 10^(3))((30)/(100)))/(3.14)` `t = 95.5s` |
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