CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2010

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

    A) \[1:1\]                                  

    B) \[2:1\]

    C) \[1:3\]                                  

    D) \[\sqrt{3}:1\]

    Correct Answer: B

    Solution :

    \[{{y}_{1}}=5[\sin 2\pi t+\sqrt{3}\cos 2\pi t]\]                 \[=10\left[ \frac{1}{2}\sin \,2\pi t+\frac{\sqrt{3}}{2}\cos 2\pi t \right]\]                 \[=10\left[ \cos \,\frac{\pi }{3}\sin \,2\pi t+\sin \frac{\pi }{3}\cos \,2\pi t \right]\]                 \[=10\,\left[ \sin \left( 2\pi t+\frac{\pi }{3} \right) \right]\] \[\Rightarrow \]    \[{{A}_{1}}=10\] Similarly,              \[{{y}_{2}}=5\sin \left( 2\pi +\frac{\pi }{4} \right)\] \[\Rightarrow \]                               \[{{A}_{2}}=5\] Hence,                  \[\frac{{{A}_{1}}}{{{A}_{2}}}=\frac{15}{5}=\frac{2}{1}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner