JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति Question Bank Self Evaluation Test - Work, Energy and Power

  • 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 m after collision?           

    A) 200mA

    B) 150 m/s

    C) 400 m/s

    D) 300 m7s

    Correct Answer: A

    Solution :

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


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