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JEE Main & Advanced Physics Elasticity Question Bank Youngs Modulus and Breaking Stress

  • question_answer
    When a certain weight is suspended from a long uniform wire, its length increases by one cm. If the same weight is suspended from another wire of the same material and length but having a diameter half of the first one then the increase in length will be                                     [CPMT 1984, 90]

    A) 0.5 cm

    B)                             2 cm

    C)                 4 cm       

    D)                 8 cm

    Correct Answer: C

    Solution :

         \[l=\frac{FL}{AY}\Rightarrow l\propto \frac{1}{{{r}^{2}}}\] (F, L and Y are constant)             \[\frac{{{l}_{2}}}{{{l}_{1}}}={{\left( \frac{{{r}_{1}}}{{{r}_{2}}} \right)}^{2}}={{(2)}^{2}}=4\]\[\Rightarrow {{l}_{2}}=4{{l}_{1}}=4cm\]


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