JEE Main 2026 · 4 Apr · Shift 1 · Physics Q34

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PhysicsSingle correct+4 / -1Question 34 of 75

A string $A$ of length 0.314 m and Young's modulus $2\times10^{10}$ N/m² is connected to another string $B$ of length and Young's modulus both twice of those of $A$ . This series combination of strings is then suspended from a rigid support and its free end is fixed to a load of mass 0.8 kg. The net change in length of the combination is ________ mm.
(radius of both the strings is 0.2 mm and acceleration due to gravity = 10 m/s²)
(Mass of both strings is to be neglected as compared to the mass of load)

1.9

Answer and worked solution

Official answer: B

Wire A. $\Delta L=\dfrac{FL}{AY}$ with $F=8$ N and $A=\pi(2\times10^{-4})^2=1.257\times10^{-7}$ m²:
$\Delta L_A=\frac{8\times0.314}{1.257\times10^{-7}\times2\times10^{10}}=1.0\times10^{-3}\text{ m}.$

Wire B doubles both L and Y, so it stretches the same 1 mm.

Total 2 mm.

(B)

Topics:Hooke's law and elastic moduli

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JEE Main 2026 · 4 Apr · Shift 1, Physics question 34