JEE Main & Advanced Physics Wave Mechanics Question Bank Self Evaluation Test - Mechanical Properties of Solids

  • question_answer
    A steel wire of length / and cross section area A is stretched by 1 cm under a given load. When the same load is applied to another steel wire of double its length and half of its cross section area, the amount of stretching (extension) is

    A) 0.5 cm

    B) 2cm

    C) 4cm     

    D) 1.5cm

    Correct Answer: C

    Solution :

    [c] Young's modulus of elasticity is \[Y=\frac{F/A}{\Delta L/L}\]       \[\therefore \Delta L=\frac{FL}{AY}\] So,  \[\Delta L\propto \frac{L}{A}\] \[\therefore \,\,\frac{\Delta {{L}_{2}}}{\Delta {{L}_{1}}}=\frac{{{L}_{2}}}{{{L}_{1}}}\times \frac{{{A}_{1}}}{{{A}_{2}}}=\frac{2}{1}\times \frac{2}{1}=4\] \[\Delta {{L}_{2}}=4\times \Delta {{L}_{1}}=4\times 1=4cm\]


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