CET Karnataka Medical CET - Karnataka Medical Solved Paper-2010

  • question_answer
    Two  simple  harmonic  motions  are represented by \[{{y}_{1}}=5\left[ \sin 2\pi t+\sqrt{3}\cos 2\pi t \right]\] and  \[~{{\text{y}}_{\text{2}}}=\text{5 sin}\left( 2\pi t\frac{\pi }{4} \right)\] The ratio of their amplitudes is

    A)  1 : 1            

    B)  2 : 1

    C)  1 : 3            

    D)  \[\sqrt{3}\]: 1

    Correct Answer: B

    Solution :

    \[{{y}_{1}}=5[sin2\pi t+\sqrt{3}cos2\pi t]\] \[=10\left[ \frac{1}{2}sin2\pi t+\frac{\sqrt{3}}{2}cos2\pi t \right]\] \[=10\left[ \cos \frac{\pi }{3}sin2\pi t+\sin \frac{\pi }{3}cos2\pi t \right]\] \[=10\left[ \sin \left( 2\pi t+\frac{\pi }{3} \right) \right]\] \[\Rightarrow \]\[{{A}_{1}}=10\] Similarly,\[{{y}_{2}}=5\sin \left( 2\pi t+\frac{\pi }{4} \right)\] \[\Rightarrow \] \[{{A}_{2}}=5\] Hence,         \[\frac{{{A}_{1}}}{{{A}_{2}}}=\frac{10}{5}=\frac{2}{1}\]


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