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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 \[120\,\,g\] is moving with a velocity of\[12\,\,m\,\,{{s}^{-1}}\]. It turns back and moves with a velocity of \[20\,\,m\,\,{{s}^{-1}}\] when hit by a bat. Find the impulse if the force acts on the ball for\[0.02\,\,s\].

    A) \[4N\,\,s\]          

    B)        \[8N\,\,s\]

    C) \[32N\,\,s\]        

    D)        \[192N\,\,s\]  

    Correct Answer: D

    Solution :

     Impulse \[=\] change in momentum             \[=m(v-u)=0.12((-20)-12)\]             \[=0.12\,\,(-32)=-3.84\,\,N\,\,s\]     Force\[\text{=}\frac{\text{Change}\,\,\text{in}\,\,\text{momentum}}{\text{Time}}\] \[=\frac{3.84}{0.02}=192\,\,N\,\,s\]


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