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NEET 2018
Exam
NEET
Year
2018
Subject
Physics
Chapter
Mechanical Properties of Solids

NEET 2018 · Physics · Mechanical Properties of Solids

Two wires are made of the same material and have the same volume....

Two wires are made of the same material and have the same volume. The first wire has cross-sectional area AA and the second wire has cross-sectional area 3A.3A . If the length of the first wire is increased by ∆l∆ l on applying a force F,F, how much force is needed to stretch the second wire by the same amount?Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the

Options

  1. A4F4F
  2. B6F6F
  3. C9F9F
  4. DFF

Correct answer

C. 9F9F

Step-by-step solution

Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the

Y=FlA∆lY = \dfrac{Fl}{A ∆ l}

∵V=Alsol=VA∵ V = Alsol = \dfrac{V}{A}

F=YA∆ll=YA2∆lVF = \dfrac{YA ∆ l}{l} = \dfrac{Y{A}^{2} ∆ l}{V}

F1F2=(A1A2)2⇒FF2=(A3A)2=19\dfrac{{F}_{1}}{{F}_{2}} = {\left(\dfrac{{A}_{1}}{{A}_{2}}\right)}^{2} ⇒ \dfrac{F}{{F}_{2}} = {\left(\dfrac{A}{3A}\right)}^{2} = \dfrac{1}{9}

F2=9F1=9F{F}_{2} = 9{F}_{1} = 9F

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