KVPY Sample Paper KVPY Stream-SX Model Paper-7

  • question_answer
    A ball is rolled over a horizontal ground making an angle of \[45{}^\circ \] with a mirror wall in an art gallery
    If velocity of ball is \[1m{{s}^{-1}}\], then velocity of image of ball with respect to ball will be

    A) \[\sqrt{2}m{{s}^{-1}}\]           

    B)  \[\sqrt{3}m{{s}^{-1}}\]

    C) \[\frac{1}{\sqrt{2}}m{{s}^{-1}}\]                    

    D) \[\frac{1}{\sqrt{3}}m{{s}^{-1}}\]

    Correct Answer: A

    Solution :

    Velocity components of object and image are as shown below.
    Clearly,\[{{\upsilon }_{object}}=\upsilon \left( -\frac{1}{\sqrt{2}}\overset{\hat{\ }}{\mathop{i}}\,+\frac{1}{\sqrt{2}}\overset{\hat{\ }}{\mathop{j}}\, \right)\]
    And \[{{\upsilon }_{image}}=\upsilon \left( -\frac{1}{\sqrt{2}}\overset{\hat{\ }}{\mathop{i}}\,+\frac{1}{\sqrt{2}}\overset{\hat{\ }}{\mathop{j}}\, \right)\]b
    Relative velocity of image with respect to
    abject is \[{{\upsilon }_{rel}}={{\upsilon }_{image}}-{{\upsilon }_{object}}\]
    \[=\sqrt{2}\,\,\upsilon \hat{i}=\sqrt{2}\,\hat{i}\,m{{s}^{-1}}\]


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