Final answer:
To find the force in member EF and determine if it's in tension or compression, apply static equilibrium and material properties equations, using information like Young's modulus, cross-sectional area, original length, and free-body diagrams as needed.
Step-by-step explanation:
To determine the force in member EF and state whether the member is in tension or compression, one must consider the conditions of static equilibrium and the properties of the material. Tension occurs when the forces applied elongate the object, while compression occurs when they shorten it. Using Figure 12.18 as a reference, we can apply the equation ΔL = (1/Y)(F/A), where ΔL is the change in length, F is the applied force, Y is Young's modulus, and A is the cross-sectional area, to calculate the amount of force exerted on member EF. If the member EF elongates, it is under tension; if it shortens, it is under compression.
The Young's modulus specific to the material of EF from Table 12.1 can be used to determine the relationship between the stress and strain in the member, and consequently, whether it is experiencing tension or compression. The cross-sectional area and the original length are necessary inputs for this calculation. If additional external forces and boundary conditions are known, a free-body diagram can be used to resolve these forces into components and apply equilibrium conditions to solve for the magnitude of force in member EF.