BVP Medical BVP Medical Solved Paper-2010

  • question_answer
    Two tuning forks A and B having a frequencyof 500 Hz each are placed with B to the rightof A. An observer is between the forks and ismoving towards B with a speed of 25 m/s.The speed of sound is 345 m/s and the windspeed is 5 m/s from A to B. Calculate thedifference in the two frequencies heard bythe observer.

    A)  72.5 Hz                                

    B)  55.6 Hz

    C)  76.2 Hz                                

    D)  80.9 Hz

    Correct Answer: A

    Solution :

                    Let the fork at A be source S^ and the fork at B be source \[\frac{m{{v}^{3}}}{4\sqrt{2g}}\]. For the sound from source \[\frac{m{{v}^{2}}}{\sqrt{2g}}\], Apparent frequency \[m(2g{{h}^{3}})\] Here \[mg\left[ \frac{b}{2} \right]\] as wind and sound are in same directions.                 \[mg\left[ a+\frac{b}{2} \right]\] \[mg\left[ \frac{b-a}{2} \right]\]               \[mg\left[ \frac{b+a}{2} \right]\] For the sound from source \[i={{i}_{1}}\cos \omega t+{{i}_{2}}\sin \omega t\] \[\frac{{{i}_{1}}+{{i}_{2}}}{2}\] as wind is opposite to sound \[\frac{{{({{i}_{1}}+{{i}_{2}})}^{2}}}{\sqrt{2}}\]                 \[\frac{1}{\sqrt{2}}\sqrt{i_{1}^{2}+i_{2}^{2}}\]                 \[\frac{i_{1}^{2}+i_{2}^{2}}{2}\] \[\Omega \]\[\frac{30.8}{\sqrt{T}}\overset{0}{\mathop{A}}\,\] As the difference is very large, the observer will not hear the beats.


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