2. A compressed-air tank having an inner diameter of 20 cm a wall thickness of 0.25 cm is formed by welding two steel hemispheres (see below).
(a) If the allowable tensile stress in the steel is 4,000 MPa, what is the maximum permissible air pressure $p_a$ in the tank?
(b) If the allowable shear stress in the steel is 6,000 MPa, what is the maximum permissible air pressure $p_b$ in the tank? (200 MPa, 571 MPa)
Weld