How does pressure change with altitude?

Pressure decreases as altitude increases. This is because the density of the air, and therefore the number of air molecules, decreases with height.

At sea level, the weight of the air above us exerts a pressure on our bodies. This is known as atmospheric pressure. As we ascend in altitude, the atmospheric pressure decreases. This is because the higher we go, the less air there is above us, and therefore, the less weight there is to exert pressure.

The atmosphere is divided into layers, and each layer has a different density. The layer closest to the Earth's surface, the troposphere, contains about 75% of the atmosphere's mass. This means it has the highest density of air molecules and therefore the highest pressure. As we ascend through the troposphere, the pressure decreases.

Once we reach the next layer, the stratosphere, the pressure continues to decrease, but at a slower rate. This is because the stratosphere is less dense than the troposphere. The same pattern continues as we ascend through the remaining layers of the atmosphere.

The change in pressure with altitude can be calculated using the barometric formula, which takes into account the height above sea level, the temperature, and the gravitational constant. However, for IGCSE Physics, it's important to understand the basic principle that pressure decreases with increasing altitude due to the decreasing density of air.

This principle has important implications for various aspects of life and science. For example, it affects the weather, as low-pressure areas often correspond to bad weather. It also affects aviation, as the decrease in pressure with altitude can impact the performance of aircraft engines and the comfort of passengers.