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

  • question_answer
    A man of mass 100 kg eats a plum cake of energy content 1470J. If he utilizes all this energy then the height to which he could lift (jump) himself is

    A)  1 m      

    B)  1.5 m

    C)  2 m                                       

    D)  9.8 m

    Correct Answer: A

    Solution :

      \[ven\frac{1}{2}m{{u}^{2}}=196\] Again, \[mgh=\frac{1}{2}m({{u}^{2}}-2\,\,gh)\] \[\Rightarrow {{u}^{2}}-2gh=2gh\Rightarrow {{u}^{2}}=2gh+2gh\] \[\Rightarrow {{u}^{2}}=4gh\Rightarrow h=\frac{{{u}^{2}}}{4g}=\frac{2\times 196}{4\times 9.8}=10\,m\,\,or\]\[0.01\,\,cm\]                              


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