The magnitude of a bending moment in a tree is influenced by which two factors?

The correct answer is based on the principles of mechanics that govern how forces affect structures, including trees. In this context, the two critical factors influencing the magnitude of a bending moment are the amount of force applied to the tree and the length of the lever arm.

The amount of force refers to the strength of the external load acting on the tree, whether from wind, ice, or any other source. The longer the lever arm—essentially the distance from the point of force application to the point where the force is resisted—the greater the bending moment that is produced. This principle is rooted in the formula for the bending moment, which is calculated as the product of the force and the distance from the pivot point (the point of resistance, such as the base of the tree).

This means that if either the force increases or the lever arm extends, the bending moment will increase proportionately. Understanding this relationship is crucial for assessing the risk of tree failure due to bending stresses.

Other factors like the degree of curvature, height of the tree, or characteristics such as age and soil composition do not directly determine the magnitude of the bending moment in the same way that force and lever arm length do, hence they are not the correct factors in this context.