JCECE Engineering JCECE Engineering Solved Paper-2010

  • question_answer
    A \[16\,\,kg\] block moving on a frictionless horizontal surface with a velocity of \[4\,\,m/s\] compresses an ideal spring and comes to rest. If the force constant of the spring be \[100\,\,N/m,\] then the spring is compressed by

    A) \[1.6\,\,m\]                       

    B) \[4\,\,m\]

    C)  \[6.1\,\,m\]                      

    D)  \[3.2\,\,m\]

    Correct Answer: A

    Solution :

    Kinetic energy of the block is                 \[K=\frac{1}{2}m{{v}^{2}}\] This kinetic energy is equal to the work done by the block before coming to rest. The work done in compressing the spring through a distance \[x\] from its normal length is                 \[W=\frac{1}{2}k{{x}^{2}}\] \[\therefore \]  \[\frac{1}{2}m{{v}^{2}}=\frac{1}{2}k{{x}^{2}}\Rightarrow x=v\sqrt{\frac{m}{k}}\] Given,\[v=4\,\,m/s,\,\,m=16\,\,kg,\,\,k=100\,\,N/m\] \[\therefore \]  \[x=4\times \sqrt{\frac{16}{100}}=1.6\,\,m\]


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