Deck General · USCG Exam Prep
Stability Definitions Practice Questions
Stability Definitions is one of the Deck Generaltopics tested on the USCG captain's license exam. Binnacle School has 8 questions on it — here are 5 to try right now, each with the correct answer and a written explanation of why.
1. Displacement is best defined as:
- A.The weight of the vessel plus all cargo, fuel, stores, and crew
- B.The weight of water displaced by the submerged volume of the hull✓
- C.The difference between lightship weight and deadweight
- D.The volume of the hull below the design waterline
Why: Displacement equals the weight of water displaced by the submerged hull. By Archimedes' principle this equals the total weight of the floating vessel. It is expressed in long tons (salt water) or metric tons.
2. Deadweight tonnage (DWT) is defined as:
- A.The weight of the empty vessel including permanent ballast and fixed equipment
- B.The total weight of water displaced at the load draft
- C.The difference between displacement at load draft and lightship displacement✓
- D.The cargo capacity expressed in cubic feet divided by 100
Why: DWT is the difference between load displacement and lightship displacement. It represents the total weight a vessel can carry: cargo, fuel, stores, water, and crew. It is not a measure of volume.
3. Freeboard is measured from the:
- A.Keel to the waterline
- B.Waterline to the top of the gunwale
- C.Load waterline to the uppermost continuous watertight deck at the vessel's side✓
- D.Keel to the metacenter
Why: Freeboard is the vertical distance from the assigned load waterline to the freeboard deck (uppermost continuous watertight deck) measured amidships at the vessel's side. Greater freeboard means greater reserve buoyancy.
4. Reserve buoyancy is best described as:
- A.The buoyancy provided by the keel and bilge keels
- B.The watertight volume of the vessel above the waterline✓
- C.The difference between displacement and deadweight
- D.The metacentric height above the keel
Why: Reserve buoyancy is the watertight volume above the waterline that can provide additional buoyancy if the vessel is forced deeper. It is essentially the freeboard volume and decreases as the vessel is loaded deeper.
5. A vessel drawing 12 feet forward and 14 feet aft in salt water is said to be:
- A.On an even keel
- B.Trimmed by the head by 2 feet
- C.Trimmed by the stern by 2 feet✓
- D.Listed 2 feet to starboard
Why: Trim = aft draft - forward draft = 14 - 12 = 2 feet. Since aft draft exceeds forward draft, the vessel is trimmed by the stern. Trim by the head would mean the bow draft is deeper than the stern.
Drill all 8 Stability Definitions questions
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