Physics Elasticity Question 95
Question: Two wires of equal lengths are made of the same material. Wire A has a diameter that is twice as that of wire B. If identical weights are suspended from the ends of these wires, the increase in length is
[EAMCET 1983; MP PMT 1990; MP PET 1995]
Options:
A) Four times for wire A as for wire B
B) Twice for wire A as for wire B
C) Half for wire A as for wire B
D) One-fourth for wire A as for wire B
Show Answer
Answer:
Correct Answer: D
Solution:
$ l=\frac{FL}{AY} $
Therefore $ l\propto \frac{1}{r^{2}} $ (F,L and Y are same) $ \frac{l _{A}}{l _{B}}={{\left( \frac{r _{B}}{r _{A}} \right)}^{2}} $
$ ={{\left( \frac{r _{B}}{2r _{B}} \right)}^{2}}=\frac{1}{4} $
Therefore $ l _{A}=4l _{B} $ or $ l _{B}=\frac{l _{A}}{4} $
BETA
