Calculate σx for ri = 1 cm
Remember elementary statics? It gives the bending stress at point O as
Using my calculator, I get σx=-101.7 MPa. We'll check the MATLAB result against this value.
Calculate σx at point O
In your program, leave a blank line and start a new section for calculating σx at point O with an explanatory comment line. Then, create the parameters M, ro, and ri since these are needed to calculate σx.
Following this is the statement to calculate I, the moment of inertia:
Things to note: the parameter pi is predefined and contains a very accurate value of π. The operator ^ is used to raise a quantity to a desired power. Now we can calculate σx at O:
The factor 10^-6^ above converts the result into MPa. The semi-colon at the end of the line is left off so that we can see what the resulting value of sigma_x is. Click on the Run icon in the editor (or hit the F5 key) . What is the value of sigma_x reported by your program? I get
This is close enough to my paper-and-pencil result of -101.7 MPa above. See my entire program here (right click and select save target as, or just left-click and copy-paste in the editor).