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NEET PHYSICSMechanical Properties of SolidsMedium

Question

Copper of fixed volume VV is drawn into a wire of length ll. When this wire is subjected to a constant force FF, the extension produced in the wire is Δl\Delta l. Which of the following graphs is a straight line?

A

Δl\Delta l vs 1/l1/l

B

Δl\Delta l vs l2l^2

C

Δl\Delta l vs 1/l21/l^2

D

Δl\Delta l vs ll

Step-by-Step Solution

  1. Young's Modulus Formula: Young's modulus (YY) is defined as the ratio of longitudinal stress to longitudinal strain: Y=F/AΔl/lY = \frac{F/A}{\Delta l/l} .
  2. Rearranging for Extension: Δl=FlAY\Delta l = \frac{Fl}{AY}.
  3. Volume Constraint: Since the volume (VV) of the wire is fixed and V=A×lV = A \times l, we can substitute the area AA with V/lV/l.
  4. Substitution: Δl=Fl(V/l)Y=Fl2VY\Delta l = \frac{Fl}{(V/l)Y} = \frac{F l^2}{VY}
  5. Analysis: Since FF, VV, and YY are constants for the given copper wire, Δl\Delta l is directly proportional to the square of the length ($
    Δll2\Delta l \propto l^2
  6. Graphical Representation: To obtain a straight line graph (y=mxy = mx), we must plot Δl\Delta l on the y-axis and l2l^2 on the x-axis. Therefore, the graph of Δl\Delta l versus l2l^2 is a straight line.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Mechanical Properties of Solids. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSMechanical Properties of Solidscoppervolumelengthsubjectedconstant

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