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WB JEE Medical WB JEE Medical Solved Paper-2007

  • question_answer
    A particle is displaced from a position\[(2\hat{i}-\hat{j}+\hat{k})\]to another position \[(3\hat{i}+2\hat{j}-2\hat{k})\] under the action of the force of \[(2\hat{i}+\hat{j}-\hat{k}).\] The work done by the force in an arbitrary unit is

    A)  8                                            

    B)  10

    C)  12                                         

    D)  16

    Correct Answer: A

    Solution :

                     Work done \[W=\vec{F}.\vec{r}\]                                 \[=(2\hat{i}+\hat{j}-\hat{k}).[3\hat{i}+2\hat{j}-2\hat{k}\] \[-(2\hat{i}-\hat{j}+\hat{k})]\] \[=(2\hat{i}+\hat{j}-\hat{k}).(\hat{i}+3\hat{j}-3\hat{k})\] \[=2+3+3\] \[=8\,\text{unit}\]


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