Fluids and Pressure

Pressure is simply how much force is applied to one area. Say, you have a cat laying on you lap and you petting it. The cat gets bored and walks away. The amount of pressure went from a large area, its body since it was laying down, to a small area, its paws. Pressure, like speed, acceleration, and momentum, can be increased or decreased. If you wanted to increase pressure on an object, you would either decrease the area you are applying it to, or increase the amount of force you are using. How are fluids related to this? Well, fluids, like everything one this planet, are made up of particles to small to see without a microscope. Water, for example, is made up of two hydrogen particles and one oxygen particle. They aren't as densely packed as a solid object, which is rigid (a good example is a tree. Try moving a full grown one without any tools). Since they are so loosely put together, its motion is random. The particles bounce into each other, away from each other, and go pretty much everywhere. If an object was dropped into a fluid, the object would be acted upon equally from all sides, constantly. Pressure is everywhere, especially in air (duh). At sea level, the air pressures roughly 2.2 pounds of pressure per square centimeter of your body. You wont notice though, since its pressuring equally from all sides. If you have ever gone in a plane, as you get higher in elevation, your ears pop. That's from the air pressure. The higher you get, the more air pressure there is. There is a lower density of breathable air as well, which is why you are in the plane and not outside it. I realize that air isn't related much to fluids, but water(or any other fluid) is a lot denser than air. Similar to the way that the pressure goes up as you get higher in the air, the pressure gets higher the farther down you go. If you went down 3300 feet without any equipment, your lungs would collapse and you would die. Its impossible to get that far down without equipment though, well, unless you were dead. Still, pressure gets higher when the elevation goes up, and gets higher the farther you go down in water.
http://www.school-for-champions.com/science/fluid_pressure.htm link