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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 6

  • question_answer
    A smooth sphere is moving on a horizontal surface with velocity vector \[2\hat{i}+2\hat{j}\] immediately before it hits a vertical wall. The wall is parallel to \[\hat{j}\] vector and the coefficient of restitution between the sphere and the wall is\[e=\frac{1}{2}\]. The velocity vector of the sphere after it hits the wall is

    A) \[\hat{i}-\hat{j}\]               

    B) \[-\hat{i}+2\hat{j}\]      

    C) \[-\hat{i}-\hat{j}\]          

    D) \[2\hat{i}-\hat{j}\]

    Correct Answer: B

    Solution :

    [b] \[\hat{j}\] component, i.e., component of velocity parallel to wall remains unchanged while \[\hat{i}\] component will become \[\left( -\frac{1}{2} \right)(2\hat{i})\] or \[-\hat{i}\]. Therefore, velocity vector of the sphere after it hits the wall is \[-\hat{i}+2\hat{j}\] .    


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