<human>:  I have a question about the book, The Physics of Buildings and Structures. How do you calculate the bending moment in a beam?
<bot>: The bending moment is the force that causes bending. The bending moment is the product of the force and the distance from the axis of the force. In the case of a beam, the force is the weight of the beam, and the distance from the axis of the force is the length of the beam.