A closely coiled helical spring is made of 10mm diameter steel wire, the coil consisting of 10 complete turns with a mean diameter of 12cm. The spring carries an axial pull of 200N. Determine the shear stress induced in the spring neglecting the effect of stress concentration. Determine also the deflection in the spring, its stiffness and the strain energy stored by it if the modulus of rigidity of the material is
0.8 $\times$106kgf / cm2.