Name A boy is whispering uniformly in all directions. that she will not be able
ID: 1574768 • Letter: N
Question
Name A boy is whispering uniformly in all directions. that she will not be able to Waves in the library. The rad the ot beabletoheahatistheminiradatedsound power fromhis mouth is 4&itspreadsout; mum distance the boy must be away from the old librarian so 5.64 m (AB) 318.3 m (BE) 200m (AD) ear him? threshold of hearing for the old librarian is 1.0x i0" w/. (AD) 56.4m (BC) 4,000 m 14. With one person was talking in a small room; & the sound intensity level was 60 dB everywhere within the room. Now, there are 8 people talking in similar manner simultaneously in the room, what is the sound intensity level? (CD) 60 dB (AB) 79 dB (BE) 72 dB (BD) 64 dB (CE) 69 dB 15. A car moving at 50 m/s approaching towards a stationary w speed is 343 m/s. What is the frequency ofsound heard by the d t emits a 440 H (AD) 384Hz (CD) 376Hz (CE) 504Hz (AE)515112 whistle that ver of the car?Explanation / Answer
13)
given power P = 4 uW = 4*10^-6 W
threshold intensity I = 1.0*10^-8 W/m^2
intensity I = P/A = P/(4*pi*r^2)
r = distance from old library
r = sqrt(P/(4*pi*I))
r = sqrt((4*10^-6)/(4*pi*10^-8))
r = 5.64 m <<<<--------------ANSWER
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14)
Intensity level B = 10*log(I/I0)
60 = 10*log(I/I0)
log(I/I0) = 6
I = 10^6*I0
for 8 people in the room
intensity I1 = 8*I = 8*10^6*I0
intensity level B1 = 10*log(I1/I0)
B1 = 10*log(8*10^6*I0/I0)
B1 = 69 dB <<<<-------------ANSWER
OPTION CE
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15)
frequency heard by driver
f = fo*(v+v0)/v
v = speed of sound
vo = speed of observer(car) = 50 m/s
f = 440*(343+50)/343
f = 504 Hz <<<<<--------ANSWER
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