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 λ.
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Question

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 λ.

G1 Physics · Accepted Answer

Use stress σ=F/A, strain ε=ΔL/L and Young's modulus Y=σ/ε. For a uniform segment, ΔL=FL/(AY); for thermal restraint, thermal strain αΔT produces stress YαΔT. Evaluating the given data/statements gives A: Loss in gravitational potential energy of M is Mgl; C: The elastic potential energy stored in the wire is 1/2 Mgl; D: Heat produced is 1/2 Mgl.. Therefore the correct answer is A, C, D.