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

  • question_answer
    A bullet of mass \[60\,\,g\] moving with a velocity of \[500\,\,m\,\,{{s}^{-1}}\] is brought to rest in 0.01 s. Find the impulse and the average force of the blow.

    A) \[-3\,\,N\,\,s,\,\,3\,\,k\,\,N\]

    B)        \[-30\,\,N\,\,s,\,\,-3\,\,k\,\,N\]  

    C) \[-50\,\,N\,\,s,\,\,-5\,\,k\,\,N\]

    D) \[-60\,\,N\,\,s,\,\,-6\,\,k\,\,N\]

    Correct Answer: B

    Solution :

     Now, impulse \[I=mv-mu=m(v-u)\] \[=0.06(0-500)=-30\,\,N\,\,s\] If \[F\] is the average force of blow, then\[I=Ft\] \[F=\frac{I}{t}=\frac{-30}{0.01}=-3,000\,\,N=-3\,\,k\,\,N\]


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