Question

What causes a percent error between the calculated value (done by a computer program like ANSYS) and the the theoretical value (done on paper) for bending stress?

Answer 1

Error can arise due to many different reasons that are often related to human error, but can also be due to estimations and limitations of devices used in measurement. ... The absolute error is then divided by the true value, resulting in the relative error, which is multiplied by 100 to obtain the percentage error.

Theoretical value is the value a scientist expects from an equation, assuming perfect or near-perfect conditions. Experimental value, on the other hand, is what is actually measured from an experiment. Rarely (in fact never) are these numbers the same.

Take the area of a sheet of paper. I know that the area of a rectangle can be found by multiplying the lengths of both sides together. I can assume an 8.5x11 sheet, so I calculate exactly 93.5 square inches. This is my theoretical value. When I actually do the measurements on my paper, it turns out my paper has been slightly cut on one end, or I’m measuring with a shoddy ruler. Therefore, I might measure only 92.8 square inches. This is my experimental value. See thats it’s close, but not exact.

Expanding on this concept, quantum mechanics is so widely accepted in the scientific community because many theoretical values calculated by mathmaticians concurred with experimental values to many, many decimal places. These would be constants such as Plank’s Constant, energy levels of harmonic potentials, and energy levels of the hydrogen atom.