NEET Solved Paper 2018 Question 44
Question: Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by $ \Delta / $ on applying a force F, how much force is needed to stretch the second wire by the same amount? [NEET - 2018]
Options:
A) 4 F
B) 6 F
C) 9 F
D) F
Show Answer
Answer:
Correct Answer: C
Solution:
For wire 1, $ \Delta \text{l=}( \frac{F}{AY} )3l $ ..(i)
For wire 2, $ \frac{\text{F }’}{3A}=Y\frac{\Delta I}{I} $
$ \Rightarrow $ $ \Delta I=( \frac{F’}{3AY} )I $ ..(ii)
From equation (i) & (ii), $ \Delta \text{I=}( \frac{F}{AY} )\text{3I=}( \frac{\text{F }’}{3AY} )I $
