Question

A 3.2 m long wire has a radius of 0.36 mm. When a 7.2 kg load is hung from it, the wire stretches 1.58 mm. What is Young’s modulus of the material of the wire?

Answer 1

Answer:

Here, l=4.0m; l=2x10-³m;

a=2.0x10-6 m² ,Y=2.0x10¹¹ N/m²

I) The energy density of stretch wire

U=1/2xstressxstrain

=1/2x2.0x10¹¹ x(2x10-³)/4)²

=0.25x10⅝=2.5x10power4 J/m³

II) Elastic potential energy = energy density x volume

=2.5x10to power4 x (2.0x10-power6)x 40J=20x 10-²=0.20J.