The bottom of a dam is made thick as:

Options

A. the water exerts low pressure on bottom wall
B. it is a custom
C. it looks beautiful
D. the water exerts more pressure on bottom of the wall

Answer

To answer the question, "The bottom of a dam is made thick as:", we need to analyze the options provided and understand the concept of pressure in fluids.

### Step-by-Step Solution:

1. **Understanding Pressure**:
- Pressure is defined as the force applied per unit area. In the context of a dam, the force comes from the weight of the water above the bottom of the dam.

2. **Identifying the Options**:
- The options given are:
1. Water exerts low pressure on bottom walls.
2. It is a custom.
3. It looks beautiful.
4. Water exerts more pressure on the bottom of the wall.

3. **Analyzing the Pressure in a Dam**:
- The pressure exerted by a fluid at a certain depth increases with depth due to the weight of the water above. The formula for pressure at a depth \( h \) is given by:
\[ P = \rho \cdot g \cdot h \]
where \( \rho \) is the density of the fluid, \( g \) is the acceleration due to gravity, and \( h \) is the depth of the fluid.

4. **Understanding Why the Bottom is Thick**:
- Since the pressure increases with depth, the bottom of the dam experiences the greatest pressure. To withstand this high pressure, the bottom of the dam is made thicker. A thicker base can support the weight of the water without collapsing.

5. **Evaluating the Options**:
- Option 1 states that water exerts low pressure on the bottom walls, which is incorrect because the pressure is high at the bottom.
- Option 2 suggests it is a custom, which does not explain the reason scientifically.
- Option 3 states that it looks beautiful, which is irrelevant to the structural integrity of the dam.
- Option 4 states that water exerts more pressure on the bottom of the wall, which is correct.

6. **Conclusion**:
- Therefore, the correct answer is option 4: "Water exerts more pressure on the bottom of the wall," which explains why the bottom of a dam is made thick.