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MGIMS WARDHA MGIMS WARDHA Solved Paper-2011

  • question_answer
    A spring scale is adjusted to read zero. Particles of mass 1 g fall on the pan of the scale and collide elastically and they rebound upward with the same speed. If the height of fall of panicles is 2 m and their rate of collision is 100 particles per second, then the scale reading in grams will be \[(g=9.8m/{{s}^{2}})\]

    A)  1000 g                                 

    B)  1100g

    C)   1200 g                                

    D)  1252 g

    Correct Answer: D

    Solution :

                     The velocity attained by particle on falling from height\[2m\]. \[v=\sqrt{2gh}=\sqrt{2\times g\times 2}=2\sqrt{g}\] Rate of change of momentum of 100 particles \[=2mv\times 100=200\text{ }mv\] From Newton's law, rate of change of momentum is equal to force. Force\[=200\text{ }mv\] \[=200\times 1\times {{10}^{-3}}\times 2\sqrt{g}\] \[=1252g\] (reading).


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