Your value of I is incorrect - please show me how you calculated it.
As I indicated back in post #14: no, it is not correct. But I really don't understand what you're trying to do - first you say the stress is 6.29, then you say its 1807, neither of which is correct. So please clarify - what paramater is the 6.29? Compressive and tensile stresses?
Ok for the new dimensions I made an error my bending moment is 8.4 not 8.33 for a start. For the new dimensions 100mmx240mm I got the I value of 1.152x10^-4. This was in turn plugged into the equation 8.4x100x10^-3/1.152x10^-4 the result was 7291.666667 which I think is 7.29x10^8
The other question I am trying to solve is this At the point of maximum stress sketch a graph of the stress
distribution through the thickness of the beam, indicating which are
tensile and compressive stresses.
It was using your equation that gave me the 6.29 results. really hoping we can solve these last two today...........
It has indeed changed. The depth of the beam has changed from 200 to 240, so the max value of y has changed from 200/2 to 240/2.
Once you get the correct max value, then yes - like I said before the stress distribution is linear, with max compressive stress at the top edge, max tensile stress at the bottom edge, and passing through 0 at the midpoint.