Final answer:
Without detailed geometric relationships between points A, B, C, and D, including distances and angles, we cannot calculate the moment vector about the line CD due to the tension force in cable AB.
Step-by-step explanation:
To determine the moment vector about the line CD due to the tension force in cable AB, we first need to establish the position vector from point C to point B and the force vector acting at point B. However, with the information provided, we're missing the critical geometric relationships between points A, B, C, and D, such as the distances and angles involved.
To calculate the moment vector (M), we would use the cross product of the position vector (r) from C to B and the tension force vector (F) acting at B, given by M = r x F. But without the specific vectors or angles, we cannot proceed with the calculation. It's important to note that the magnitude of M would depend not only on the magnitude of the tension force (80 lb) but also on the perpendicular distance from the line CD to the line of action of the force.