In Figure 4 a ring weight W = 2 kN slides freely on a vertical steel rod hanging from the ceiling and is dropped through h = 10 mm onto the collar at the lower end. Taking the work done by the falling weight as W(h + δ), where δ is the extension of the rod, determine (a) the maximum instantaneous stress in the rod (in MPa), (b) the maximum extension of the rod (in mm) and (c) the strain energy stored in the rod at that instant (in J).