What happens to stress if the boom arm is made longer while keeping material constant?

Stress is defined as the force applied to an object divided by the area over which the force is applied. When the boom arm is made longer, the same force will be applied over a greater length.

While the length is increased, the cross-sectional area remains the same if the material is kept constant. Therefore, if the same force is applied to this longer boom, the distribution of that force over the area remains unchanged—it doesn’t change the amount of stress. However, increasing the length can lead to a larger moment arm if torque is involved, meaning the material could experience greater bending or torsional stress due to additional moments acting on it.

Thus, if the load applied remains constant, the stress itself can increase due to changes in the load conditions and internal responses of the material. In a typical scenario for the boom arm, longer lengths experience more significant bending moments, which can effectively increase stress, supporting the reasoning for the selection that stress increases with a longer arm.