KVPY Sample Paper KVPY Stream-SX Model Paper-20

  • question_answer
    A ball of mass m, moving with a speed of \[2{{v}_{0}}\] collides in elastically with an identical ball at rest.
    Now, choose the correct option.

    A) For a general head on collision first ball retraces its path backwards

    B) For a general head on collision first ball stops after collision

    C) For a general head on collision angle between velocities of scattered balls is \[90{}^\circ \]

    D) For a general head on collision angle between velocities of scattered balls is less than \[90{}^\circ \]

    Correct Answer: D

    Solution :

    By conservation of momentum,
    \[{{p}_{i}}={{p}_{1}}+{{p}_{2}}\]
    For a general collision, some energy is lost
    \[\Rightarrow \]\[\frac{p_{i}^{2}}{2m}>\frac{p_{1}^{2}}{2m}+\frac{p_{2}^{2}}{2m}\]\[\Rightarrow \]\[{{p}^{2}}>p_{1}^{2}+p_{2}^{2}\]
    \[\therefore \]      \[\theta <90{}^\circ \]


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