suspended rod

Problem 206
A steel rod having a cross-sectional area of 300 mm² and a length of 150 m is suspended vertically from one end. It supports a tensile load of 20 kN at the lower end. If the unit mass of steel is 7850 kg/m³ and E = 200 × 10³ MN/m², find the total elongation of the rod.
 

Problem 205
A uniform bar of length L, cross-sectional area A, and unit mass ρ is suspended vertically from one end. Show that its total elongation is δ = ρgL²/2E. If the total mass of the bar is M, show also that δ = MgL/2AE.