All questions of Pressure for UPSC CSE Exam

Understanding Fluid Pressure
Fluid pressure is influenced by various factors. The pressure exerted by a fluid depends primarily on its density, depth, and the acceleration due to gravity. Here’s a breakdown of each factor:
1. Density of the Fluid
- The greater the density of the fluid, the higher the pressure it exerts at a given depth.
- High-density fluids (like mercury) exert more pressure compared to low-density fluids (like water) at the same depth.
2. Depth of the Fluid
- Pressure increases with depth in a fluid due to the weight of the fluid above.
- The deeper you go, the more fluid there is above you, leading to increased pressure.
3. Acceleration Due to Gravity
- The pressure exerted by a fluid is directly proportional to the gravitational force acting on it.
- A stronger gravitational pull (like on a planet with higher gravity) will result in higher fluid pressure at the same depth.
4. Temperature of the Fluid
- While temperature affects properties like density, it does not directly impact the pressure exerted at a given depth in a static fluid.
- Changes in temperature can alter fluid density, but for static fluids, pressure remains unchanged unless density changes.
Conclusion
In conclusion, temperature does not directly affect fluid pressure under static conditions, making it the correct answer to the question. The other factors—density, depth, and gravitational acceleration—are crucial in determining fluid pressure.

Explanation:
The pressure exerted by the water increases when a person dives deep into a swimming pool. This can be explained by the concept of hydrostatic pressure.

Hydrostatic Pressure:
- Hydrostatic pressure is the pressure exerted by a fluid at equilibrium due to the force of gravity.
- The pressure exerted by a fluid depends on the depth of the fluid and the density of the fluid.
- As a person dives deeper into the water, they experience an increase in the depth of the fluid above them.
- The increase in depth results in an increase in the weight of the water above the person, leading to an increase in pressure.

Increasing Pressure:
- The deeper a person dives into the swimming pool, the greater the amount of water above them, resulting in higher pressure.
- The increased pressure can be felt by the person diving as they descend deeper into the pool.
- This increase in pressure is why divers have to equalize their ears to prevent discomfort or injury due to the changing pressure.
Therefore, when a person dives deep into a swimming pool, the pressure exerted by the water increases due to the greater depth of the fluid above them, resulting in higher hydrostatic pressure.

Understanding Atmospheric Pressure
Atmospheric pressure refers to the weight of the air above a given point in the atmosphere. This pressure is influenced by various factors, with altitude being a significant one.
Why Option B is Correct
- Decrease with Altitude: As you ascend in altitude, the amount of air above you decreases. This results in less weight pressing down, which leads to a decrease in atmospheric pressure.
- Density of Air: The density of air is higher at lower altitudes because the air molecules are packed more closely together due to gravitational pull. As altitude increases, the air becomes thinner, contributing to lower pressure.
Examples of Atmospheric Pressure Changes
- Mountains: At the top of a mountain, such as Mount Everest, the atmospheric pressure is significantly lower than at sea level. Climbers often experience difficulty breathing due to this reduced pressure.
- Weather Patterns: Weather patterns are influenced by changes in atmospheric pressure. High-pressure systems are typically associated with clear skies, while low-pressure systems can lead to cloudy and rainy conditions.
Conclusion
In summary, atmospheric pressure is not constant and decreases with increasing altitude. This phenomenon is essential for understanding weather, climate, and even aviation, where changes in pressure can affect flight safety and efficiency.