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3 years ago

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A police car travels towards a stationary observer at a speed of 15m/s. the siren on the car emits a sound of frequency 250Hz. C

alculate the observer frequency. the speed of sound is 340m/s

1 answer:

skelet666 [1.2K]3 years ago

7 0

Observer Frequency = sound frequency x ( speed of sound / speed of sound - speed of car)

= 250 x (340/( 340-15))

= 261.54 Hz

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Explanation:

a)

The speed of a standing wave on a string is given by

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where

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In this part of the problem, the tension in the string is doubled, so that the new tension is

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Substituting into the equation, we find the new speed of the wave in the string:

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b)

We can solve also this part by referring to the formula

$v=\sqrt{\frac{T}{m/L}}$

where

T is the tension

m is the mass

L is the length

In this case, the string mass is quadrupled, so the new mass is:

m' = 4m

Substituting into the equation, we find what happens to the speed of the wave:

$v'=\sqrt{\frac{T}{m'/L}}=\sqrt{\frac{T}{4m/L}}=\frac{1}{\sqrt{4}}\sqrt{\frac{T}{m/L}}=\frac{1}{2}v$

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c)

Again, we can solve this part by referring to the same equation

$v=\sqrt{\frac{T}{m/L}}$

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m is the mass

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$v'=\sqrt{\frac{T}{m/L'}}=\sqrt{\frac{T}{m/(4L)}}=\sqrt{4}\sqrt{\frac{T}{m/L}}=2v$

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Answer:

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