Please I need help with these questions, I need to study them for my exam. Thank
ID: 1491754 • Letter: P
Question
Please I need help with these questions, I need to study them for my exam. Thanks in advance :)
12. -12 points Walker4 14.P030 My Notes When you drop a rock into a well you hear the splash 2.6 seconds later (a) How deep is the well? (b) If the depth of the well were doubled, would the time required to hear the splash be greater than, less than, or equal to 5.2 seconds? -Selectv 13. + -12 points Walker4 14.P.034 My Notes The distance to a point source is increased by a factor of 6. (a) By what multiplicative factor does the intensity decrease? b) By what additive amount does the intensity level decrease? dB 14. + -11 points Walker4 14.P044 My Notes A person with perfect pitch sits on a bus bench listening to the 437 Hz horn of an approaching car. If the person detects a frequency of 473 Hz, how fast is the car moving? m/sExplanation / Answer
1.
A. T = 2.6 sec
T = Tup + Tdown
T = d/v + sqrt(2d/g)
2d/g = (T - d/v)^2
T = 2.6 sec,
v = speed of sound = 343 m/sec
g = 9.81 m/sec^2
2*d/9.81 = (2.6 - d/343)^2
d = 30.89 m
B.
if D = 2d, then T' will be
T' = D/v + sqrt(2D/g)
T' = 2d/v + sqrt(4d/g)
T' = 2d/v + sqrt(2)*sqrt(2d/g)
2T = 2d/v + 2*sqrt(2d/g)
T' is not equal to 2T, it is less then 2T
2.
A. intensity is proportional to 1/r^2
if distance is 6 times than intensity will be
decreased by 1/36 times
B.
for intensity level
dB = 10*log (I/I0)
dB = 10*log (1/36) = -15.56
it means initial intensity is 15.56 dB times greater.
3.
f' = f*(v - vo)/(v - vs)
vo = 0
vs = ?
v = 343 m/sec
f' = 473 Hz
f = 437 Hz
473 = 437*(343 - 0)/(343 - vs)
vs = 26.10 m/sec