CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2002

  • question_answer
    For any vector\[\overrightarrow{a},\hat{i}\times (\overrightarrow{a}\times \hat{i})+\hat{j}\times (\overrightarrow{a}\times \hat{j})\]\[+\hat{k}\times (\overrightarrow{a}\times \hat{k})\]is equal to:

    A)  \[\overrightarrow{0}\]                                

    B)                         \[\overrightarrow{a}\]

    C)                         \[2\overrightarrow{a}\]              

    D)                         \[3\overrightarrow{a}\]

    E)                         \[4\overrightarrow{a}\]

    Correct Answer: C

    Solution :

                     \[\hat{i}\times (\overrightarrow{a}\times \hat{i})+\hat{j}\times (\overrightarrow{a}\times \hat{j})+\hat{k}(\overrightarrow{a}\times \hat{k})\] \[=(\hat{i}.\hat{i})\overrightarrow{a}-(\hat{i}.\overrightarrow{a})\hat{i}+(\hat{j}.\hat{j})\overrightarrow{a}-(\hat{j}.\overrightarrow{a})\hat{j}\]                                                 \[+(\hat{k}.\hat{k})\overrightarrow{a}-(\hat{k}.\overrightarrow{a})\hat{k}\] \[=3\overrightarrow{a}-\overrightarrow{a}=2\overrightarrow{a}\]


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