The longitudinal extension of any elastic material is very small. In order to have an appreciable change, the material must be in the form of

Options

A. short thin wire
B. thin block of any cross-section
C. long thin wire
D. thick block of any cross-section

Answer

C

Explanation

`Y = (MgL)/(pi r^(2)(Delta L)) :. (Delta L) = (MgL)/(pi r^(2) Y)`
Thus for an appreciable change in length in the same wire and for the same load, L should be large and r should be small i.e. a long thin wire should be used.