If a beam is free to move on its supports with no additional forces, what type of support does it have?

A beam that is free to move on its supports without any additional forces is considered to have simple supports. In structural engineering, simple supports allow for rotation but not for vertical displacement. This means that the beam can expand or contract freely due to temperature changes or other conditions, while still being supported on both ends.

The concept of simple supports is fundamental in mechanics and structural analysis because it simplifies the calculation of reactions and moments in static equilibrium situations. With this type of support, each end of the beam can lift freely if the load is removed, which is a characteristic of simply supported beams, distinguishing them from fixed supports that would restrain movement and rotation.

Understanding the nature of supports is crucial for determining how forces and moments are distributed throughout a structure, which is essential for ensuring stability and safety in engineering designs. Other support types, such as those mentioned in the incorrect options, do not accurately describe the condition of free movement as seen in simple supports.