Q: Steel is more elastic than Rubber . Why ?
Sol: Consider a Steel and a rubber wire of same length (L) , Same cross-sectional area (A) .
As we know , Young’s Modulus of Elasticity , $\displaystyle Y = \frac{F L}{A \Delta L}$
If same force (F) be applied on both the wires ,
For Steel , $\displaystyle Y_s = \frac{F L}{A \Delta L_s}$ ….(i)
For Rubber , $\displaystyle Y_r = \frac{F L}{A \Delta L_r}$ ….(ii)
On dividing ,
$\displaystyle \frac{Y_s}{Y_r} = \frac{\Delta L_r}{\Delta L_s}$
As for same force applied , ΔLr > ΔLs
$\displaystyle \frac{Y_s}{Y_r} = \frac{\Delta L_r}{\Delta L_s} > 1 $
Thus , Ys > Yr
Hence , Steel is more elastic than Rubber .