# What will increase when air pressure goes up?

Pressure reduces with height: As altitude increases, pressure lowers. The total weight of the air above a unit area at any height can be interpreted as pressure at any altitude in the atmosphere. There are fewer air molecules over a given surface at higher elevations than at lower heights. For example, there are 730 millimeters (29 inches) of water vapor in one kilogram (2.2 pounds) of water at sea level, but only 511 millimeters (20 inches) at 10,000 feet elevation.

The density of air decreases with increasing elevation or pressure: At constant temperature, this means that there is less mass of air per unit volume at high altitudes than at low levels. This effect explains why high-altitude winds are usually lighter than low-level winds of the same speed; it takes more energy to drive these winds because there is less matter with which to work.

At sea level, an airplane flying directly upward has enough kinetic energy to rise another 12 miles (19 km). But at 50,000 feet (15,000 m), the plane would need to fly at about 500 miles per hour (800 km/hr) to stay airborne for a minute! At these speeds, even a small aircraft would mean devastation for anyone on board. The force of wind blowing against an airplane is called its drag, and the faster you go the more drag you produce.

## Does pressure increase or decrease with height?

As the height of a surface above ground level increases, so does atmospheric pressure. This is because the quantity of air molecules reduces as altitude increases. A surface has less air above it. So there are more molecules per unit area and thus greater pressure.

At any given temperature, pressure will be inversely proportional to height. That is, as you go up, the pressure will drop.

This is because there are fewer particles per volume of air at higher altitudes. The average distance between particles (i.e., air density) decreases as you go up.

So, pressure decreases with height.

Note that this relationship applies only if there is no change in temperature along with height. If there is a change in temperature then you need to consider that variable too.

For example, if you went from cold to hot as you ascended, then pressure would likely rise along with height because there are more gas molecules when it's hot out.

Finally, don't forget to include your explanation on why pressure increases or decreases with height. This is important for accurate calculations using Boyle's Law.

## Why does air pressure always decrease with increasing height above the surface?

The weight of the air is reduced. This means that objects cannot be supported as high up in the atmosphere.

This effect explains why air pressure decreases with increasing elevation or altitude. If you travel by plane, you have probably noticed that air pressure decreases when you climb higher. This is because there is less air at higher elevations than at lower levels. As air pressure decreases, so does the amount of force exerted on an object below the surface of the earth.

The human body is well adapted to these changes in air pressure. We don't feel any difference between sea level and 10,000 feet above sea level (because our blood is pumped around by large vessels located near the surface of the body), but anything more than this elevation can cause problems for those who travel in aircraft.

When you go up in altitude, there is less air available to exert force on objects below you. This means that you need to supply less force in order to lift the same object at higher elevations. As long as your force is equal to the weight of the object, then it will remain at its current position. But if your force is not enough, then the object will fall back to the ground.

## Why does the air pressure decrease as we go up?

Because the majority of the molecules in the atmosphere are confined close to the earth's surface by gravity, air pressure declines fast at first, then more slowly at higher heights. At an altitude of 10,000 feet (3,048 m), for example, there are about half as many molecules in the air than at sea level.

The number of air molecules is called the atmospheric density. The force of attraction between two particles is inversely proportional to the distance between them. So, as you go up, the density of the air decreases, and the force of attraction between any two particles increases, which causes them to come closer together.

This means that objects near the top of the atmosphere will be pressed together harder than objects near the ground. For example, if you were to take a pile of sand on the beach and press it down with a heavy book, it would spread out until it reached its maximum height. But if you repeated this experiment at the top of a high mountain, the book would only push the pile so far before it popped back up because of the increased force of gravity.

This is why astronauts aboard the space station experience less pressure when they lift their legs off the floor or float in their modules: They're not exerting enough force against the surrounding atmosphere to make a difference.

##### Randy Alston

Randy Alston is a journalist and has been working in the media industry for over 20 years. He's a graduate of Syracuse University's School of Journalism where he studied magazine publishing. He's been with The Times Union ever since as a writer, editor, or publisher. His favorite part of his job is reporting on important issues that affect people's lives in the Capital Region.

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