JEE Advanced 2013 · Paper 1 · Physics Q9

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PhysicsSingle correct+2Question 9 of 60

One end of a horizontal thick copper wire of length $2L$ and radius $2R$ is welded to an end of another horizontal thin copper wire of length $L$ and radius $R$ . When the arrangement is stretched by applying forces at two ends, the ratio of the elongation in the thin wire to that in the thick wire is

0.25

0.50

2.00

4.00

Answer and worked solution

Official answer: C

Same tension in both. $\Delta L=\dfrac{FL}{AY}$ :

thin: $\dfrac{FL}{\pi R^2Y}$
thick: $\dfrac{F(2L)}{\pi(2R)^2Y}=\dfrac{FL}{2\pi R^2Y}$

Ratio 2.

(C)

Topics:Hooke's law and elastic moduli

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JEE Advanced 2013 · Paper 1, Physics question 9