NEET Sample Paper NEET Sample Test Paper-75

  • question_answer
    If a force \[\operatorname{F}=6{{t}^{2}} \hat{i}+4t\,\hat{j}\] is acting on a particle of mass 3kg, then velocity of particle at \[\operatorname{t}= 3s\] is (at \[\operatorname{t} =0\], particle is at rest)

    A)  \[2\hat{i} + 3\hat{j}\]              

    B)  \[4\hat{i} + 6\hat{j}\]

    C)  \[18\hat{i} + 6\hat{j}\]             

    D)  None of these

    Correct Answer: C

    Solution :

    Here, \[\operatorname{F}=6{{t}^{2}}\hat{i}\,\,+\,\,4t\,\hat{j}\] \[m=3\,kg\] \[\therefore \,\,\,\,\,\,Acceleration\,\,\,a=\frac{F}{m}=\frac{6{{t}^{2}}\,\hat{i}+4t\,\hat{j}}{3}=2{{t}^{2}}\,\hat{i}+\frac{4}{3}t\,\hat{j}\]As,            \[a=\frac{dv}{dt}\] \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\,\,dv=adt=(2{{t}^{2}}\,\hat{i}\,\,+\,\,\frac{4}{3}t\,\hat{j})\,dt\] \[\int{dv=\int_{0}^{3}{\left( 2{{t}^{2}}\,\hat{i}+\frac{4}{3}\,{{t}^{2}}\,\hat{j} \right)}\,\,}dt\] \[v=\left[ \frac{2}{3}{{t}^{3}}\,\hat{i}\,\,+\,\,\frac{4}{6}{{t}^{2}}\,\hat{j}\, \right]_{0}^{3}\] \[v\,\,=\,\,18\,\hat{i}\,\,+\,\,6\,\hat{j}\]


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