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 `l`.
A. Loss in gravitinal potential energy of `M` is `Mgl`
B. Elastic potential energy stored in the wire is `(Mgl)/(2)`
C. Elastic potential energy stored in the wire is `Mgl`
D. Elastic potential energy stored in the wire is `Mgl//3`

Answer 1

Correct Answer - A::B
The wire experinces offers an average resisting force of `(0 + mg)/(2) = (mg)/(2)`
The remaining `(mgl)/(2)` energy is lost because of internal resistance with in the wire.