BHU PMT BHU PMT (Mains) Solved Paper-2005

  • question_answer

    Directions: In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:

    A body of mass M is attached to the lower end of a metal wire, whose upper end is fixed. The elongation of the wire is\[l\]. (1) Loss in gravitational potential energy of M is\[Mgl\] (2) The elastic potential energy stored in the wire is\[\frac{1}{2}Mgl\] (3) The elastic potential energy stored in the wire is\[Mgl\] (4) Heat produced is\[\frac{1}{2}Mgl\]

    A)  1 and 2 are correct

    B)  2 and 3 are correct

    C)  1 and 4 and correct

    D)  1, 2 and 4 are correct

    Correct Answer: D

    Solution :

                     When a body of mass M is attached to the lower end of a metal wire whose upper end is fixed and the elongation of wire is\[l\], then loss in gravitational potential energy of mass\[m=MgL\]As elastic potential energy stored in stretched wire \[=\frac{Mgl}{2}\] Hence, heat produced in wire                 \[=Mfl-\frac{Mgl}{2}=\frac{Mgl}{2}\]


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