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9th Class Science Work and energy Question Bank Work Power and Energy Summative Objective Problems

  • question_answer
    A body of mass 2kg moving up has potential energy 400J and kinetic energy 580J at a point 'P' in its path. The maximum height reached by the body is (\[\text{g}=\text{1}0\text{m}{{\text{s}}^{-\text{2}}}\])

    A)  49 m    

    B)  98 m

    C)  196 m                  

    D)  392 m

    Correct Answer: A

    Solution :

      \[m=2kg,g=10\,m/{{s}^{2}}.\] If the maximum height reached by the body is ?h?. On reaching it, its \[P.E.=mgh\] This should be equal to the total energy at any instant. i.e., \[mgh=400\,J+580J=980J\] \[\Rightarrow 2\times 10\times h=980\Rightarrow h=\frac{980}{20}=49\,m\]                     


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