2. Solved Papers
  3. RAJASTHAN PMT

RAJASTHAN PMT Rajasthan - PMT Solved Paper-2005

  • question_answer
    An iron bar of length \[l\] and having a cross-section A is heated from 0 to \[100{}^\circ C\]. If this bar is so held that it is not permitted to expand or bend/ the force that is developed, is:

    A)  inversely proportional to the cross-sectional area of the bar

    B)  independent of the length of the bar

    C)  inversely proportional to the length of the bar

    D)  directly proportional to the length of the bar

    Correct Answer: B

    Solution :

    When force F is applied \[\Upsilon =\frac{FL}{Al}\]where \[\Upsilon \] is Youngs modulus, A  is area \[F=\frac{\Upsilon Al}{L}\]            ...(1) From the formula for linear expansion                                   \[\alpha =\frac{l}{L\times 100}\]                      ...(2) According to the condition mat bar will not bend or expand Now from equations (1) and (2) \[F=\Upsilon A\times 100\,\alpha \] Hence, force is independent of length L


You need to login to perform this action.
You will be redirected in 3 sec spinner