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

  • question_answer
    Two wires of equal lengths are made of the same material. Wire A has a diameter that is twice as that of wire B. If identical weights are suspended from the ends of these wires, the increase in length is [EAMCET 1983; MP PMT 1990; MP PET 1995]

    A) Four times for wire A as for wire B

    B)                 Twice for wire A as for wire B

    C)                 Half for wire A as for wire B

    D)                 One-fourth for wire A as for wire B

    Correct Answer: D

    Solution :

        \[l=\frac{FL}{AY}\]Þ \[l\propto \frac{1}{{{r}^{2}}}\] (F,L and Y are same)             \[\frac{{{l}_{A}}}{{{l}_{B}}}={{\left( \frac{{{r}_{B}}}{{{r}_{A}}} \right)}^{2}}\]\[={{\left( \frac{{{r}_{B}}}{2{{r}_{B}}} \right)}^{2}}=\frac{1}{4}\]Þ \[{{l}_{A}}=4{{l}_{B}}\] or \[{{l}_{B}}=\frac{{{l}_{A}}}{4}\]


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