A Thin-Walled Spherical Tank Has a Diameter of 0 $20 \mathrm { MPa }$

Multiple Choice

A thin-walled spherical tank has a diameter of 0.75 m and an internal pressure of 20 MPa. The yield $20 \mathrm { MPa }$ stress in tension is 920 MPa, the yield stress in shear is 475 MPa, and the factor of safety is 2. $475 \mathrm { MPa }$ of elasticity is 210 $\text { GPa, }$ Poisson's ratio is 0.28, and maximum normal strain is $1220 \times 10 ^ { - 6 }$ The minimum permissible thickness of the tank is approximately:

A) $8.6 \mathrm {~mm}$
B) $9.9 \mathrm {~mm}$
C) $10.5 \mathrm {~mm}$
D) $11.1 \mathrm {~mm}$