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

  • question_answer
    A wire of length 2 m is made from \[10\ c{{m}^{3}}\] of copper. A force F is applied so that its length increases by 2 mm. Another wire of length 8 m is made from the same volume of copper. If the force F is applied to it, its length will increase by                          [MP PET 2003]

    A) 0.8 cm

    B)             1.6 cm

    C)             2.4 cm

    D)                      3.2 cm

    Correct Answer: D

    Solution :

        \[l=\frac{FL}{AY}=\frac{F{{L}^{2}}}{(AL)Y}=\frac{F{{L}^{2}}}{VY}\] \ \[l\propto {{L}^{2}}\] If volume of the wire remains constant             \[\frac{{{l}_{2}}}{{{l}_{1}}}={{\left( \frac{{{L}_{2}}}{{{L}_{1}}} \right)}^{2}}={{\left( \frac{8}{2} \right)}^{2}}=16\] \\[{{l}_{2}}=16\times {{l}_{1}}=16\times 2=32mm=3.2cm\]


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