A wave is traveling at 6 m/s on a string with a linear density of 0.084 kg/m wha
ID: 1412990 • Letter: A
Question
A wave is traveling at 6 m/s on a string with a linear density of 0.084 kg/m what is the tension in the string The decibel level 0 of a jack hammer is 127dB relative to the threshold of hear*. Determine the sound intensity I produced by the jack hammer in (W/m^2)? A Car Is moving at 40m/s approaches a stationary whistle that emits a f=240H2 sound. The speed of sound is 343 m/s. what is the frequency of sound heard by the driver of the car? (The source of the sound is stationary). What would be the observed frequency if the whistling source was moving 40m/s toward the car while the car was at rest? (The observer is stationary).Explanation / Answer
Problem 6)
The expression for the velocity of a wave is
v = f
= v /f
= 31 / 58
= 0.534 m
correct answer d
Problem 7)
The expression for a wave on a string is
v = sqrt (T/)
T = v2
T = 62 0.084
T = 3.024 N
Problem 8)
The expression for decibel
= 10 log (I/Io)
= 10 log (117 / 1 10-12) = 10 (12) log 117
= 248 d
P = I1 A1 = I2 A2
I1/I2 = A2/A1= 4 R22 /4 R12 = R22 /R12
I1 = 117 W/m²
R1 = 4m
R2 = 10 m
I2 = I1 (R1/R2)2
I2 = 117 (4/10)2
I2 = 18.72 W/m²
Problem 9)
= 10 log (I/Io)
/10 = log (I/Io)
100.1 = I/Io
I = Io 100.1
I = 1 10-12 100.1 127
I = 10-12 5 1012
I = 5 W/m²
Problem 10)
This is a problem of Doppler effect
stationary source
f'= ((v+vo)/v ) f
f' = ( ( 343 + 40)/343 ) 240 = 1.1166 240
f' = 267.99 Hz
Moving source
f'= (v / (v - vs) ) f
f'= ( 343/(343- 40) ) 240 = 1.132 240
f'= 271. 68 Hz