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JEE Main & Advanced JEE Main Paper (Held on 7 May 2012)

  • question_answer
    A particle gets displaced by\[\Delta \over line{r}=\left( 2\hat{i}+3\hat{j}+4\hat{k} \right)m\]under the action of a force\[\vec{F}=\left( 7\hat{i}+4\hat{j}+3\hat{k} \right).\]The change in its kinetic energy is     JEE Main Online Paper (Held On 07 May 2012)

    A) 38 J                                        

    B)                        70J

    C)                        52.5 J                    

    D)                        126 J

    Correct Answer: A

    Solution :

                    According to work-energy theorem, Change in kinetic energy = work done \[=\vec{F}.\Delta \vec{r}=\left( 7\hat{i}+4\hat{j}+3\hat{k} \right).\left( 2\hat{i}+3\hat{j}+4\hat{k} \right)\] \[=14+12+12=38J\]


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