NEET Sample Paper NEET Sample Test Paper-19

  • question_answer 19) A force \[\vec{F}=3\hat{i}-2\hat{j}+4\hat{k}\]displaces an object from a point P (1, 1, 1) to another point Q (2, 0, 3). The work done by force is:

    A)  10 J              

    B)  12 J

    C)  13 J              

    D)  None of these

    Correct Answer: C

    Solution :

    \[{{\vec{r}}_{1}}=\hat{i}+\hat{j}+\hat{k}\] and \[{{\vec{r}}_{2}}=2\hat{i}+3\hat{k}\] \[\therefore \]\[\Delta \vec{r}={{\vec{r}}_{2}}-{{\vec{r}}_{1}}=2\hat{i}+3\hat{k}-\hat{i}-\hat{j}-\hat{k}\] \[=\hat{i}-\hat{j}+2\hat{k}\] \[W=\vec{F}.d\vec{r}\] \[=(3\hat{i}-2\hat{j}+4\hat{k}).(\hat{i}-\hat{j}+2\hat{k})\] \[=3+2+8=13\,J\] Hence, the correction option is[c].

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