Physics Elasticity Question 142
Question: A force F is applied on the wire of radius r and length L and change in the length of wire is l.If the same force F is applied on the wire of the same material and radius 2r and length 2L, Then the change in length of the other wire is
[RPMT 1999]
Options:
A) l
B) 2l
C) l/2
D) 4l
Show Answer
Answer:
Correct Answer: C
Solution:
$ l=\frac{FL}{AY}\Rightarrow l\propto \frac{L}{r^{2}} $ (F and Y are constant) $ \frac{l _{2}}{l _{1}}=\frac{L _{2}}{L _{1}}\times {{\left( \frac{r _{1}}{r _{2}} \right)}^{2}}=2\times {{\left( \frac{1}{2} \right)}^{2}}=\frac{1}{2} $
$ \
Therefore l _{2}=\frac{l _{1}}{2} $ i.e. the change in the length of other wire is $ \frac{l}{2} $
BETA
