WB JEE Medical WB JEE Medical Solved Paper-2007

  • question_answer
    The recoil velocity of a 4.0 kg rifle that shoots a 0.050 kg bullet at a speed of \[280\,\text{m}{{\text{s}}^{-1}}\] is

    A)  \[+\,3.5\,m{{s}^{-1}}\]                 

    B)  \[-\,3.5\,m{{s}^{-1}}\]

    C)  \[-\sqrt{(3.5)}m{{s}^{-1}}\]                        

    D)  \[+\sqrt{(3.5)}\,m{{s}^{-1}}\]

    Correct Answer: B

    Solution :

                     \[{{m}_{1}}{{u}_{1}}+{{m}_{2}}{{u}_{2}}=0\] \[\Rightarrow \]               \[{{u}_{1}}=-\frac{{{m}_{2}}{{u}_{2}}}{{{m}_{1}}}\]                 \[=-\frac{0.050\times 280}{4}=-3.5\,\text{m}{{\text{s}}^{-1}}\]


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