Exam Question

### **Calculation of Percentage Variation in Daily Fuel Consumption**
#### **1. Governing Principle**
The relationship between a ship's speed and its main engine fuel consumption is governed by the **Cube Law**. This principle states that the fuel consumed per unit of time (e.g., tonnes per hour) is approximately proportional to the cube of the ship's speed through the water.
* **Rationale:** A ship's total resistance is primarily composed of frictional resistance and wave-making resistance. As speed increases, wave-making resistance increases significantly, approximately with the square of the speed. Since Power = Resistance × Velocity, the required power to overcome this resistance varies approximately with the cube of the velocity ($$ P \propto V^3 $$). As fuel consumption is directly proportional to the power produced by the engine, it also follows this cubic relationship.