**The Pressure Exerted by Water on the Bottom of the Tank**

**Introduction:**
When water is contained in a tank, it exerts pressure on the walls and the bottom of the tank. The pressure exerted by water depends on the depth of the water and the density of water. In this case, we have a tank with dimensions 2m x 4m x 2m and the water has a density of 1000 kg/m^3. Let's calculate the pressure exerted by water on the bottom of the tank.

**Formula:**
The pressure exerted by a fluid at a certain depth can be calculated using the formula:

Pressure = density x gravity x height

Where:
- Pressure is the force exerted per unit area (in Pascals)
- Density is the mass of the fluid per unit volume (in kg/m^3)
- Gravity is the acceleration due to gravity (approximately 9.8 m/s^2)
- Height is the depth of the fluid (in meters)

**Calculation:**

**Step 1:**
We need to find the depth of the water in the tank. Since the tank has a height of 2m, the depth of the water can be assumed as 2m.

**Step 2:**
Using the given density of water (1000 kg/m^3), gravity (9.8 m/s^2), and the depth of the water (2m), we can substitute these values into the formula to calculate the pressure:

Pressure = 1000 kg/m^3 x 9.8 m/s^2 x 2m
Pressure = 19600 N/m^2 (Pascals)

**Conclusion:**
The pressure exerted by water on the bottom of the tank is 19600 Pascals. This pressure is the force exerted by the water per unit area. It is important to note that the pressure exerted by a fluid increases with the depth of the fluid and the density of the fluid. In this case, the pressure is directly proportional to the depth of the water, the density of water, and the acceleration due to gravity.