JEE Main & Advanced Sample Paper JEE Main - Mock Test - 11

  • question_answer
    A bullet of mass 20g and moving with 600 m/s collides with a block of mass 4 kg hanging with the string. What is velocity of bullet when it comes out of block, if block rises to height \[0.2\text{ }m\] after collision?

    A) \[200 m/s\]                     

    B) \[150 m/s\]

    C) \[400 m/s\]                     

    D) \[300 m/s\]

    Correct Answer: A

    Solution :

    Initial, \[K.E.=\frac{1}{2}m{{v}^{2}}=\frac{1}{2}\times \frac{20}{1000}\times 600\times 600=3600\,J\]
    Change in \[K.E.=P.E.\]
    \[\frac{1}{2}m({{v}^{2}}-v{{'}^{2}})=mgh\]
    \[\Rightarrow \,\,3600-\frac{1}{2}\times \frac{20}{1000}\times {{v}_{1}}^{2}=4\times 10\times 80\]
    \[\Rightarrow \,\,\,\,{{v}_{1}}=200m/s\]


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