Civil Engineering Professional Engineer Practice Exam

Which type of force causes a material to sag?

1. Shear force

2. Compression

3. Bending force

4. Torsion

The correct answer is: Bending force

The type of force that causes a material to sag is bending force. When a beam or any structural member is subjected to bending, it experiences a combination of compression and tension along different sections of its length. Specifically, the upper portion of the beam typically undergoes compression, while the lower part experiences tension. This differential distribution of stress ultimately results in the material bending or sagging under the applied load. Bending occurs primarily due to external loads being applied perpendicular to the length of the member, leading to a curvature that reflects the sagging behavior. Understanding this principle is vital for civil engineers, as it directly impacts the design and analysis of structures to ensure they can withstand the forces they encounter without excessive deflection or structural failure.