Final answer:
The main tension member of a truss between the supports is known as the bottom chord or lower chord.
Step-by-step explanation:
The main tension member of a truss running along the lower side, between the supports is called the bottom chord or lower chord. In the context of structural engineering, tension is a force that stretches materials and is critically important in the design of structures like trusses. The bottom chord experiences tension as it elongates under the applied loads.
This concept can be visualized through the example of a tightrope walker, where the wire creates tension to support the weight of the walker. The wire, although affected by the walker's weight, experiences a tension with upward components on each side (the left tension T₁ and the right tension TR). The tension in the bottom chord serves a similar structural function in a truss, providing stability and support.