🔍 Key Concepts
• Thrust between barges when going ahead is carried by couplings that pull one barge forward by another, not by lines whose main job is just to hold position.
• Compare springs between tug and barges (control fore‑and‑aft movement of the tug) with side or cross‑coupling wires between barges (let the outer barge share the push).
• Look carefully at the direction each line leads: which one is aligned so that when the inside barge is pushed ahead, that line will pull another barge along in the same direction?
đź’ Think About
• When the tow is moving ahead, how does the outer barge that is NOT directly against the tug receive pushing force? Trace the load path from the tug to that barge across the lines in the picture.
• Which labeled item connects one barge to another in such a way that tension in that line would pull the second barge forward, rather than just holding it alongside or preventing it from drifting away?
• For each choice (B, E, H, I), imagine the towboat applies power ahead: which line would tighten up to drag another barge forward, and which lines would mainly act as springs or position‑keeping lines?
âś… Before You Answer
• For each option, check: Does this line run generally in the fore‑and‑aft direction between two barges? If not, it is less likely to carry ahead thrust.
• Verify which items run from barge to barge, and which run from tug to barge; only the former can transmit thrust from one barge to another.
• Ask: if the center barge suddenly stopped, which line would become heavily loaded as it tried to keep the other barge moving ahead with it? That’s the type of line this question is referring to.