JEE Main & Advanced Physics Two Dimensional Motion JEE PYQ - Two Dimensional Relative Motion

  • question_answer
    The position co-ordinates of a particle moving in a 3-D coordinate system is given by
    \[~x=a\text{ }cos\omega t\]
    \[y=a\text{ }sin\omega t\] and \[z=a\omega t\]
    The speed of the particle is: [JEE Main 09-Jan-2019 Evening]

    A) \[a\omega \]

    B) \[\sqrt{3}\,a\omega \]

    C) \[\sqrt{2}\,a\omega \]

    D) \[2\,a\omega \]

    Correct Answer: C

    Solution :

    [c] \[{{V}_{x}}=a\omega sin\omega t\]
    \[{{V}_{y}}=a\omega cos\omega t\]
    \[{{V}_{z}}=a\omega \]
    \[\left| V \right|=\sqrt{V_{x}^{2}+V_{y}^{2}+V_{z}^{2}}\]
    \[=\,\sqrt{{{a}^{2}}{{\omega }^{2}}\,{{\sin }^{2}}\,\omega t+{{a}^{2}}{{\omega }^{2}}\,{{\cos }^{2}}\,\omega t\,+{{a}^{2}}\,{{\omega }^{2}}}\]
    \[\left| V \right|\,\,=\,\,\sqrt{2}\,a\omega \]


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