Class 4 (4th Engineer) SC&S 📅 Jun 2025

Exam Question

(a) Explain why the draught of a ship decreases when it passes from fresh water to seawater and vice versa. (6)

(b) A lock gate which is 15m. wide has salt water on one side to a depth of 8m. and fresh water on the other side to a depth of 9m. Find the resultant thrust on the lock gate and the state on which side of the gate it acts. (10)

Reference Answer

### (a) Change in Draught with Water Density (6 Marks)
**1. Fundamental Principle: Archimedes' Principle**
A ship floats because it displaces a volume of water that has a weight equal to the ship's own weight. This weight is referred to as the ship's displacement (Δ).
**2. The Relationship Between Displacement, Volume, and Density**

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