Question A$2$:

A compressed air tank having an inner diameter of $18$ meters and a wall thickness of $$ meter is formed by welding two steel hemispheres $($see Figure QA$2).$

$($a$)$ If the allowable tensile stress in the steel is $14000$ Pa$,$ what is the maximum permissible air pressure in the tank?

$[5$ Marks$]$

$($b$)$ If the allowable shear stress in the steel is $6000$ Pa$,$ what is the maximum permissible pressure?

$[5$ Marks$]$

$($c$)$ If the normal strain in the outer surface of the tank is not to exceed $0\mathrm{.}0003,$ what is the maximum permissible pressure? $($Assume Hooke$$s law is obeyed E $=29$ MN$/$m$2$ and Poisson$$s ratio is

u $=0\mathrm{.}28)$