NEET Sample Paper NEET Sample Test Paper-50

  • question_answer 19) Force acting on a particle is\[\left( 2\widehat{i}+3\widehat{j} \right)N\]. Work one by this force is zero, when a particle is moved on the line\[3y+kx=5\]. Here value of k is-

    A) 2                                 

    B) 4

    C) 6                                 

    D) 8

    Correct Answer: A

    Solution :

    Force is parallel to a line \[y=\frac{3}{2}\,\,x\,\,+\,\,c\] The equation of given line can be written as \[y=-\frac{k}{3}\,x\,\,+\,\,\frac{5}{3}\] Work done will be zero, when force is perpendicular to the displacement i.e., the above two lines are perpendicular or \[{{m}_{1}}{{m}_{2}}=-1\] or \[\left( \frac{3}{2} \right)\left( -\frac{k}{3} \right)\,\,=\,\,-1\] \[k=2\]

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