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

  • question_answer
    When a uniform wire of radius r is stretched by a 2kg weight, the increase in its length is 2.00 mm. If the radius of the wire is r/2 and other conditions remain the same, the increase in its length is        [EAMCET (Engg.) 2000]

    A) 2.00 mm

    B)                      4.00 mm

    C)             6.00mm

    D)                      8.00 mm

    Correct Answer: D

    Solution :

                    \[l=\frac{FL}{\pi {{r}^{2}}Y}\therefore l\propto \frac{1}{{{r}^{2}}}\] (F,L and Y are constant)             \[\frac{{{l}_{2}}}{{{l}_{1}}}={{\left( \frac{{{r}_{1}}}{{{r}_{2}}} \right)}^{2}}={{(2)}^{2}}\Rightarrow {{l}_{2}}=4{{l}_{1}}=4\times 2=8\ mm.\]


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