NEET Sample Paper NEET Sample Test Paper-83

  • question_answer
    The length of a metal wire is \[{{L}_{1}}\] when the tension in it is \[{{T}_{1}}\,and\,\,{{L}_{2}}\] when tension in it is \[{{T}_{2}}\]. The original length of the wire is

    A)  \[\frac{\sqrt{{{T}_{1}}{{T}_{2}}}}{{{L}_{1}}+{{L}_{2}}}\]             

    B)  \[\frac{{{T}_{1}}{{L}_{1}}\,-\,\,{{T}_{2}}{{L}_{2}}}{{{T}_{1}}+{{T}_{2}}}\]

    C)  \[\frac{{{T}_{2}}{{L}_{1}}\,-\,\,{{T}_{1}}{{L}_{2}}}{{{T}_{2}}-{{T}_{1}}}\]                     

    D)  \[\frac{{{T}_{1}}{{L}_{1}}\,-\,\,{{T}_{2}}{{L}_{2}}}{{{T}_{1}}+{{T}_{2}}}\]

    Correct Answer: C

    Solution :

    Let \[\operatorname{L} =original length of wire\] \[\therefore \,\,\,\,\,\,\,\,\,\Delta {{L}_{1}}={{L}_{1}}-L\] Similarly, change in length of second wire is \[\Delta {{L}_{2}}={{L}_{2}}-L\] Now, \[Y=\frac{{{T}_{1}}}{A}\times \frac{L}{\Delta {{L}_{1}}}=\frac{{{T}_{2}}}{A}\times \frac{L}{\Delta {{L}_{2}}}\] \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\frac{{{T}_{1}}}{\Delta {{L}_{1}}}\,=\frac{{{T}_{2}}}{\Delta {{L}_{2}}}\] \[\frac{{{T}_{1}}}{{{L}_{1}}-L}\,=\frac{{{T}_{2}}}{{{L}_{2}}-L}\] \[L=\frac{{{T}_{2}}{{L}_{1}}-{{T}_{1}}{{L}_{2}}}{{{T}_{2}}-{{T}_{1}}}\]


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