Solve Speed of Car Given 36% Horn Drop: 340m/s Sound Speed

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SUMMARY

The problem involves calculating the speed of a car based on a 36% drop in the frequency of its horn as it passes an observer, with the speed of sound given as 340 m/s. The correct formula to use is f' = f(v/(v - v_source), which accounts for the Doppler effect when the source is moving toward and then away from the observer. The initial attempt to solve for the speed of the car resulted in an incorrect value due to misapplication of the formula and unit conversion errors. The final answer must be expressed in kilometers per hour (km/h).

PREREQUISITES
  • Understanding of the Doppler effect in sound waves
  • Familiarity with the formula f' = f(v/(v - v_source))
  • Ability to convert units from meters per second to kilometers per hour
  • Basic algebra skills for solving equations
NEXT STEPS
  • Review the principles of the Doppler effect in physics
  • Practice solving problems involving the Doppler effect with varying frequencies
  • Learn how to convert between different units of speed, specifically m/s to km/h
  • Explore additional examples of sound wave frequency changes due to motion
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Students studying physics, particularly those focusing on wave mechanics and the Doppler effect, as well as educators looking for practical examples to illustrate these concepts.

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Homework Statement



Find the speed of a car if the tone of the horn drops by 36 percent as it passes you. The speed of sound is 340 m/s. Answer in units of km/h.

Homework Equations



f'=f(v/(v-v_source))

solce for v source.



The Attempt at a Solution



I thought I would just set .36f = f (340/(340-x)) and solve for x (x= -604.4) this is not the right answer.
 
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luna02525 said:
Find the speed of a car if the tone of the horn drops by 36 percent as it passes you. The speed of sound is 340 m/s. Answer in units of km/h.

f'=f(v/(v-v_source)

It drops by 36% in comparison to the frequency it had before passing you.

The formula you've written above is incorrect, if it is for the moving away part.

You have to consider both the source coming toward you initially and then receding.

And, of course, the change in units, as mentioned in the last post.
 

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