NEET Sample Paper NEET Sample Test Paper-1

  • question_answer 4) A force \[\vec{F}=3\hat{i}+c\hat{j}+2\hat{k}\] acting on a particle cause a displacement \[\vec{S}=-4\hat{i}+2\hat{j}+3\hat{k}\] in its own direction. If the work done is 6J, then the value of c will be:

    A)  12                  

    B)  6

    C)  1                    

    D)  0

    Correct Answer: B

    Solution :

    Given,     Force    \[\vec{F}=3\hat{i}+c\hat{j}+2\hat{k}\] Displacement     \[\vec{S}=-\,4\hat{i}+2\hat{j}+3\hat{k}\] Work done                   \[W=6\,J\] and workdone is given by             \[W=\vec{F}\times S\] \[\Rightarrow \]               \[6=\left( 3\hat{i}+c\hat{j}+2\hat{k} \right)\,.\,\left( 4\hat{i}+2\hat{j}+3\hat{k} \right)\] \[\Rightarrow \]               \[6=-12+2c+6\] \[\Rightarrow \]               \[6=-6+2c\] \[\Rightarrow \]               \[2c=12\] \[\Rightarrow \]               \[c=6\]

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