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

  • question_answer
    If K.E. of a given particle is doubled, its momentum will be

    A)  double                                

    B)  tripled                         

    C)  increases by \[\sqrt{2}\]times

    D)  remains unchanged.

    Correct Answer: C

    Solution :

      Given, \[K.{{E}_{1}}=K.E.\]and \[K.{{E}_{2}}=2K.E{{.}_{1}}\] The body is same therefore ?m? is constant. We know, \[K.E.=\frac{{{p}^{2}}}{2m}\] \[\Rightarrow K.E.\,\,\,\alpha \,\,{{P}^{2}}\]                       (\[\because \]?m? is same) \[\therefore \,\,K.E{{.}_{1}}=p_{1}^{2}\Rightarrow {{P}_{1}}=\sqrt{K.{{E}_{1}}}\]                             ?????(1) \[\,\,K.E{{.}_{2}}=P_{1}^{2}\Rightarrow \sqrt{K.{{E}_{2}}}\Rightarrow {{P}_{2}}=\sqrt{2K.E{{.}_{1}}}\]     ?????(2)                                 \[(\because \,\,K.E{{.}_{2}}=2K.{{E}_{1}})\] Dividing equation (2) by (1) we get, \[\frac{{{P}_{2}}}{{{P}_{1}}}=\frac{\sqrt{K.E{{.}_{1}}}}{\sqrt{2K.E{{.}_{2}}}}=\frac{1}{\sqrt{2}}\] \[\therefore \]Momentum is increaded by\[\sqrt{2}\]times.


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