An open-coiled helical spring has 20 coils of wire of diameter 10 mm at a pitch of 80 mm, the coils having a mean radius of 120 mm. if the spring is subjected to an axial twist of 5 nm, find the maximum normal and shear stress in the section of the wire. if e- 200 gpa and g 80 gpa, determine the axial extension of the spring and the relative rotation between the ends. find the strain energy stored in the spring,