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9th Class Science Force and laws of motion Question Bank Force and Laws of Motion

  • question_answer
    A cricket ball of mass \[500\,\,g\] is moving with a speed of\[36\,\,km\,\,{{h}^{-1}}\]. It is reflected with the same speed. What is the impulse applied on it?

    A) \[20\,\,kg\,\,m\,\,{{s}^{-1}}\]    

    B)        \[5\,\,kg\,\,m\,\,{{s}^{-1}}\]

    C) \[25\,\,kg\,\,m\,\,{{s}^{-1}}\]    

    D)        \[10\,\,kg\,\,m\,\,{{s}^{-1}}\]  

    Correct Answer: D

    Solution :

    \[m=500\,\,g=0.5\,\,kg\] \[u=36\,\,km\,\,{{h}^{-1}}=10\,\,m\,\,{{s}^{-1}};\,\,v=-10\,\,m\,\,{{s}^{-1}}\] Now, impulse\[=mv-mu=m(v-u)\] \[=0.5[-10-10]=0.5\times -20=-10\,\,kg\,\,m\,\,{{s}^{-1}}\].


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