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J & K CET Engineering J and K - CET Engineering Solved Paper-2013

  • question_answer
    The  scalar product of two vectors \[A=2\hat{i}+2\hat{j}-\hat{k}\] and \[B=-\hat{j}+\hat{k},\] is given by

    A)  \[A.B=3\]          

    B)  \[A.B=4\]

    C)  \[A.B=-4\]        

    D)  \[A.B=-3\]

    Correct Answer: D

    Solution :

    Given, \[A=2\hat{i}+2\hat{j}-\hat{k}\] and \[B=-\hat{j}+\hat{k}\] Scalar product \[A.B=(2\hat{i}+2\hat{j}-\hat{k}).(-\hat{j}+\hat{k})\] Using  \[\hat{i}.\hat{i}=1,\,\,\hat{j}.\hat{j}=1,\,\hat{k}.\hat{k}=1\]=1we have \[A.B=-2-1=-3\]


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