NEET AIPMT SOLVED PAPER 2003

  • question_answer
                    When a long spring is stretched by 2 cm, its potential energy is U. If the spring is stretched by 10 cm, the potential energy in it will be:                                                                                                                      

    A)                 10 U

    B)                 25 U      

    C)                 U/5       

    D)                 5 U

    Correct Answer: B

    Solution :

                           Potential energy in a stretched spring is given by                 \[U=\frac{1}{2}k\,{{x}^{2}}\]                 \[\therefore \frac{{{U}_{1}}}{{{U}_{2}}}={{\left( \frac{{{x}_{1}}}{{{x}_{2}}} \right)}^{2}}\]                 Given, \[{{x}_{1}}=2\,cm\,=0.02\,m,\,\,{{x}_{2}}=10\,cm=0.1\,m\]                 Substituting the values, we have                 \[\frac{{{U}_{1}}}{{{U}_{2}}}={{\left( \frac{0.02}{0.1} \right)}^{2}}={{\left( \frac{1}{5} \right)}^{2}}=\frac{1}{25}\]                 \[\Rightarrow {{U}_{2}}=25\,{{U}_{1}}=25\,U\]


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