Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Tonnage is a measure of ship's capacity. It can be expressed either in volume or weight.
Reason (R): Displacement tonnage is the amount of water displaced by a ship expressed in tons weight (1ton = 1000kg i.e. 0.99m$^3$ of salt water or 1m$^3$ of fresh water).
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Gross Tonnage (GT) and Net Tonnage (NT) are volume measurements (100 cubic feet per ton), while Displacement and Deadweight are actual weight measurements (metric tons).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
"Tonnage" in naval architecture is a complex term that can refer to volume (as in Gross Tonnage) or weight (as in Displacement). It is the fundamental metric for determining a ship's size, carrying capacity, and its impact on the water.
Detailed Explanation:
Analysis of Assertion (A): Historically, tonnage was a measure of the volume of "tuns" (wine barrels) a ship could carry. Today, it describes the internal volume (Gross/Net Tonnage) or the actual weight of the ship (Displacement Tonnage). Thus, it is a measure of capacity expressed in volume or weight units. Therefore, (A) is true.

Analysis of Reason (R): Based on Archimedes' Principle, a floating ship displaces an amount of water equal to its own weight. "Displacement Tonnage" is literally the weight of the water displaced. The standard values provided ($1\text{m}^3$ of freshwater = 1 ton; salt water is denser so $\approx 0.97\text{--}0.99\text{m}^3 = 1$ ton) are accurate physical constants. Therefore, (R) is true.

Evaluating the Relationship: The Reason (R) provides the physical definition of one of the types of tonnage mentioned in the Assertion (A). By explaining how weight-based tonnage is calculated through water displacement, it provides the scientific explanation for the weight aspect of the ship's capacity measurement.

Step 2: Final Answer:
Both statements are true and the reason explains the physical basis for weight-based tonnage.