Final answer:
To determine the force in member ED and assess whether it's in tension or compression, one must calculate the stress on the member, analyze the deformations, and utilize Young's modulus. Tension causes elongation, while compression results in contraction. The force is determined based on the equilibrium of forces and material behavior.
Step-by-step explanation:
To determine the force in member ED of the truss, one needs to analyze the forces acting on the truss and apply concepts of tension and compression. These concepts relate to the ways in which materials deform under the action of forces, with tension referring to a force that attempts to elongate a material and compression referring to a force that attempts to shorten it. According to the given information, when an object is in either tension or compression, the net force on it is zero, but it deforms by changing its original length Lo. The deformation can be quantified in terms of tensile or compressive stress and strain, using Young's modulus for the material, as indicated by the linear relationship between stress and strain.
Applying this to member ED, one must calculate the tensile or compressive stress acting on it. The next step is to use the linear relationship between stress and strain along with Young's modulus value to find the elongation or contraction of the member, which would indicate whether the member is in tension or compression. If the change in length (AL) is positive, the member is in tension; if negative, it's in compression. This analysis is dependent on the equilibrium of forces, implying that the member will be in either tension or compression when the forces balance each other out.