Physics Elasticity Question 126
Question: When a weight of 10 kg is suspended from a copper wire of length 3 metres and diameter 0.4 mm, its length increases by 2.4 cm. If the diameter of the wire is doubled, then the extension in its length will be
[MP PMT 1994]
Options:
A) 9.6 cm
B) 4.8 cm
C) 1.2 cm
D) 0.6 cm
Show Answer
Answer:
Correct Answer: D
Solution:
$ 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}}={{\left( \frac{1}{2} \right)}^{2}}\Rightarrow l _{2}=\frac{l _{1}}{4}=\frac{2.4}{4} $
$ \Rightarrow l _{2}=0.6\ cm $
BETA
