JEE Main & Advanced Physics NLM, Friction, Circular Motion Question Bank Second Law of Motion

  • question_answer
    A body of mass 8kg is moved by a force \[F=3x\,N,\] where \[x\] is the distance covered. Initial position is \[x=2\,m\] and the final position is \[x=10\]m. The initial speed is \[0.0m/s.\] The final speed is                                [Orissa JEE 2002]

    A)             6 m/s  

    B)             12 m/s

    C)             18 m/s

    D)             14 m/s

    Correct Answer: A

    Solution :

                    Increment in kinetic energy = work done             Þ \[\frac{1}{2}m({{v}^{2}}-{{u}^{2}})=\int_{{{x}_{1}}}^{{{x}_{2}}}{F.dx}=\int_{2}^{10}{(3x)\ dx}\]             Þ \[\frac{1}{2}m{{v}^{2}}=\frac{3}{2}[{{x}^{2}}]_{2}^{10}=\frac{3}{2}[100-4]\]             Þ \[\frac{1}{2}\times 8\times {{v}^{2}}=\frac{3}{2}\times 96\] Þ \[v=6m/s\]


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