How do crew members control the density of a submarine?

Explanation

To control the density of a submarine, crew members utilize a system of tanks that can be filled with air or water. Here’s a step-by-step explanation of how this process works:

### Step 1: Understanding Density
- **Concept of Density**: Density is defined as mass per unit volume. An object will float if its overall density is less than that of the fluid it is in (in this case, water) and will sink if its density is greater.

### Step 2: The Role of the Main Ballast Tank
- **Ballast Tank Function**: The main ballast tank of a submarine is crucial for controlling its buoyancy. It can be filled with air or water to adjust the overall density of the submarine.

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