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JEE Main 202227 JulyEvening Shift
Exam
JEE Main
Year
2022
Date
27 July
Shift
Evening Shift
Subject
Physics
Chapter
Mechanical Properties of Solids

JEE Main 2022 · 27 July · Evening Shift · Physics · Mechanical Properties of Solids

A steel wire of length 3 . 2m( Y _ S = 2 . 0 × 10 ^ 11 N m ^ - 2 )...

A steel wire of length 3.2m(YS=2.0×1011Nm−2)3 . 2m\left({Y}_{S} = 2 . 0 \times {10}^{11}N{m}^{- 2}\right) and a copper wire of length 4.4m(YC=1.1×1011Nm−2)4 . 4m\left({Y}_{C} = 1 . 1 \times {10}^{11}N{m}^{- 2}\right) , both of radius 1.4mm1 . 4mm are connected end to end. When stretched by a load, the net elongation is found to be 1.4mm1 . 4mm. The load applied, in Newton, will be: (Given π=227\pi = \dfrac{22}{7})A steel wire of length 3 . 2m( Y _ S = 2 . 0 × 10 ^ 11 N m ^ - 2 ) and a copper wire of length 4 . 4m( Y _ C = 1 . 1 ×

Options

  1. A360360
  2. B180180
  3. C10801080
  4. D154154

Correct answer

D. 154154

Step-by-step solution

A steel wire of length 3 . 2m( Y _ S = 2 . 0 × 10 ^ 11 N m ^ - 2 ) and a copper wire of length 4 . 4m( Y _ C = 1 . 1 ×

When two wires are connected end to end, the tension in them will be same.

Change in length using Hooke's law can be found as,

Y=FlA∆l⇒\Deltal=FlAYY = \dfrac{Fl}{A ∆ l} ⇒ \Deltal = \dfrac{Fl}{AY}

Total change in length can be written as,

\Deltal=Δl1+Δl2\Deltal = \Delta{l}_{1} + \Delta{l}_{2}

⇒\Deltal=Fl1A1Y1+Fl2A2Y2⇒ \Deltal = \dfrac{F{l}_{1}}{{A}_{1}{Y}_{1}} + \dfrac{F{l}_{2}}{{A}_{2}{Y}_{2}}

⇒F=\Deltall1A1Y1+l2A2Y2=1.4×10−33.2π(1.4×10−3)2×2.0×1011+4.4π(1.4×10−3)2×1.1×1011⇒F=1.54×102=154N⇒ F = \dfrac{\Deltal}{\dfrac{{l}_{1}}{{A}_{1}{Y}_{1}} + \dfrac{{l}_{2}}{{A}_{2}{Y}_{2}}} = \dfrac{1 . 4 \times {10}^{- 3}}{\dfrac{3 . 2}{\pi{\left(1 . 4 \times {10}^{- 3}\right)}^{2} \times 2 . 0 \times {10}^{11}} + \dfrac{4 . 4}{\pi{\left(1 . 4 \times {10}^{- 3}\right)}^{2} \times 1 . 1 \times {10}^{11}}} ⇒ F = 1 . 54 \times {10}^{2} = 154N

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