1. The problem statement, all variables and given/known data From the solution , it's clear that the top part of the beam undergo tension , while the lower part undergo compression . 2. Relevant equations 3. The attempt at a solution But , i dont understand why it is so . When the moment is applied in the horizontal axis , the structure will slide become like this , right ? ( the top part will be slided into the book ) I cant imagine how the moment applied causing the top part to experience tension , while the lower part experience compression .