9th Class Science Work and energy Question Bank Work, Energy and Power

  • question_answer
    The potential energy of a certain spring when stretched through a distance 'S' is 10 joules. The amount of work (in joule) that must be done on this spring to stretch it through an additional distance "S" will be

    A)  30                           

    B)         40

    C)  10                         

    D)         20

    Correct Answer: A

    Solution :

                    \[u=\frac{1}{2}K{{s}^{2}}\] \[\Rightarrow \]               \[10=\frac{1}{2}K{{s}^{2}}\]                                         ? (i) Work done,\[W=\frac{1}{2}K{{(2s)}^{2}}-\frac{1}{2}K{{s}^{2}}\]                 \[=2K{{s}^{2}}-\frac{1}{2}K{{s}^{2}}\]                 \[=\frac{3}{2}K{{s}^{2}}\] From equation (i), we get \[W=3\times 10=\mathbf{30}\]joules.


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