Question

A wire of cross-sectional area 4 x 10^-4 m², modulus of rigidity 2 x 10¹¹ Nm^-2 and length 1 m is stretched between two vertical rigid poles. A mass of 1 kg is suspended at its middle. Calculate the angle it makes with horizonal.

Answer 1

In fig., for equilibrium position of mass m

Mg = 2T sinθ    ...(i)

If θ is small, sinθ = θ = x/L  ...(ii)

As T = YA/L x ΔL = YA/L[(L² + x²)^1/2 - L]

= YAx²/2l²    ...(iii)

Hence,