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

  • question_answer
    A stone projected vertically upwards from the ground reaches a maximum height h. When it is at a height 3h/4, the ratio of its kinetic and potential energies is

    A)  3 : 4                      

    B)  1 : 3

    C)  4 : 3                                      

    D)  3 : 1

    Correct Answer: B

    Solution :

      P.E at height\['h'=mgh\] P.E at height\[\frac{3h}{4}=\frac{3mgh}{4}\] K.E at the height of\[\frac{3h}{4}=P.E.\]at maximum height ?h? - P.E at the height                 \[\frac{3h}{4}=mgh-\frac{3mgh}{4}=\frac{1}{4}mgh\] \[\therefore \]Ratio between K.E and P.E at the height of 3h/4 \[=\frac{mgh\times 4}{4\times 3\,\,mgh}=1:3\]


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