Let the body be hung from the middle point C so that it sags through 1 cm to the point D as shown in the figure

∴ AD^{2} = AC^{2} + CD^{2} = (50)^{2} + (1)^{2}

or AD = 50.01 cm

Increase in length = 0.01

Strain = 0.01/50 = 2 x 10^{-4}

Stress = 2 × 10^{12} × 2 × 10^{–4}

= 4 × 10^{8} dynes/cm^{2}

Tension T = Stress × Area of cross-section

= 4 × 10^{8} × π × (0.08)^{2}

Since the mass m is in equilibrium,

mg = 2T cosθ or m = 2T cosθ/g