AFMC AFMC Solved Paper-2000

  • question_answer
    In a transverse progressive wave of amplitude A, the maximum panicle velocity is four times its wave velocity, then the wavelength of the wave is:

    A) \[2\pi A\]                            

    B) \[\pi A\]

    C)  \[\frac{\pi A}{2}\]                                          

    D)  \[\frac{\pi A}{4}\]

    Correct Answer: C

    Solution :

                     Key Idea: When particle passes through its equilibrium position, then the velocity is maximum. Velocity of a body changes with displacement \[(y),u=\omega \sqrt{{{A}^{2}}-{{y}^{2}}}\]where A is amplitude, \[\omega \] is angular frequency. When particle passes through its equilibrium position, then the velocity is maximum \[{{u}_{\max }}=A\omega \] Given,     \[{{u}_{\max }}=4v\] \[\therefore \]   \[4v=A\omega \] \[\Rightarrow \]    \[\omega =\frac{4v}{A}\] From the relation, speed = frequency \[\times \] wavelength We have \[\text{Wavelength = }\frac{\text{speed}}{\text{frequency}}\] Also, \[\omega \,\,=2\pi n,\,\]where n is frequency Hence,     \[n=\frac{\omega }{2\pi }\] Putting this value in Eq. (i), we have \[Wavelength=\frac{v}{\omega /2\pi }=\frac{v}{4v/A2\pi }\]                 \[\lambda =\frac{\pi A}{2}\]


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