Physics Elasticity Question 78
Question: When a certain weight is suspended from a long uniform wire, its length increases by one cm. If the same weight is suspended from another wire of the same material and length but having a diameter half of the first one then the increase in length will be
[CPMT 1984, 90]
Options:
A) 0.5 cm
B) 2 cm
C) 4 cm
D) 8 cm
Show Answer
Answer:
Correct Answer: C
Solution:
$ l=\frac{FL}{AY}\Rightarrow l\propto \frac{1}{r^{2}} $ (F, L and Y are constant) $ \frac{l _{2}}{l _{1}}={{\left( \frac{r _{1}}{r _{2}} \right)}^{2}}={{(2)}^{2}}=4 $
$ \Rightarrow l _{2}=4l _{1}=4cm $
BETA
