A strain gage is installed as shown on an aluminum soda can. The can's radius is 1.3 in and its wall thickness is 0.004 in (sometimes written as 4 mil; 1 mil = 1/1000 in). When the lid of the can is opened, the magnitude of the strain reading changes by 180 μstrain.
a. What was the internal pressure p in the can?
b. When the can was pressurized, what was the factor of safety with respect to yielding in the cylindrical wall?