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  3. RAJASTHAN ­ PET

RAJASTHAN ­ PET Rajasthan PET Solved Paper-2001

  • question_answer
    An Indian rubber cord L metre long and area of cross-section A metre2 is suspended vertically. Density of rubber is\[D\text{ }kg/{{m}^{2}}\]and Young's modulus of rubber is\[E\text{ }n/{{m}^{2}}\]. If the wire extends by 1 m under its own height; then extension in length / is

    A)  \[{{L}^{2}}Dg/E\]

    B)  \[{{L}^{2}}Dg/2E\]

    C)  \[{{L}^{2}}Dg/4E\]

    D)  \[L\]

    Correct Answer: B

    Solution :

     Elongation in a card by its own weight, which act at the centre of gravity of the card. Force \[F=mg=V\text{ }Dg=ALDg\] Elongation of length, \[l=\frac{FL/2}{YA}\] \[\frac{{{L}^{2}}Dg}{2EA}=\frac{{{L}^{2}}Dg}{2E}\]


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