CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    A massless spring of natural length of 0.5 m and spring constant 50 N/m has one end fixed and the other end attached to a mass of 250 g. The spring mass system is on a smooth floor. The mass is pulled until the length of the spring is 0.6 and then released from rest. The kinetic energy of the mass when the length of the spring is 0.5 m is:

    A)  0.25 J                   

    B)         2.25 J

    C)  6.25 J                   

    D)         9 J

    E)  25 J

    Correct Answer: A

    Solution :

    The kinetic energy of spring mass system is \[K=\frac{1}{2}m{{\omega }^{2}}({{a}^{2}}-{{y}^{2}})\] where \[\omega =\frac{2\pi }{T}=\frac{2\pi }{2\pi }\sqrt{\frac{K}{m}}=\sqrt{\frac{K}{m}}\] Given, \[m=250\text{ }g=250\times {{10}^{-3}}kg,\]                                 \[\omega =\sqrt{\frac{50}{250\times {{10}^{-3}}}}\]                 \[{{a}^{2}}-{{y}^{2}}={{10}^{-2}}\] \[\therefore \]  \[K=\frac{1}{2}\times 250\times {{10}^{-3}}\times 100\times 2\times \frac{1}{100}\]                 \[K=0.25\,J\]


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