JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति Question Bank Work Done by Constant Force

  • question_answer
    A body of mass 6kg is under a force which causes displacement in it given by \[S=\frac{{{t}^{2}}}{4}\] metres where t is time. The work done by the force in 2 seconds is           [EAMCET 2001]

    A)             12 J    

    B)             9 J

    C)             6 J      

    D)             3 J

    Correct Answer: D

    Solution :

                    \[s=\frac{{{t}^{2}}}{4}\] \\[ds=\frac{t}{2}dt\] \[F=ma=\frac{m{{d}^{2}}s}{d{{t}^{2}}}=\frac{6{{d}^{2}}}{d{{t}^{2}}}\left[ \frac{{{t}^{2}}}{4} \right]\ =\ 3N\] Now \[W=\int_{0}^{2}{F\,ds}=\int_{0}^{2}{3\frac{t}{2}dt}=\frac{3}{2}\left[ \frac{{{t}^{2}}}{2} \right]_{0}^{2}=\frac{3}{4}\left[ {{(2)}^{2}}-{{(0)}^{2}} \right]=3J\]         


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