# What is meant by static pressure?

Say it out loud: The force per unit area exerted by a fluid on a surface that is at rest relative to the fluid. This is also called "static" pressure.

Static pressure is the pressure that fluids exert against their boundaries. Static pressure depends on the weight of the fluid, its density, and the surface tension between the fluid and its container.

For example, if you were to take a glass of water and put your hand over the mouth of the glass, you would feel the weight of the liquid above your hand and thus know that it is under static pressure. This pressure will be greater as the volume of fluid increases or if it is a heavy fluid such as water.

Also, if the container has openings (such as a tube) then some of the fluid will leak out which reduces the static pressure.

Static pressure can be either higher or lower than atmospheric pressure depending on the shape of the container and how much volume it contains.

For example, if you were to fill a glass up to its brim with water and placed your hand over the top of the glass, you would feel no pressure because there is no difference between inside and outside the glass and thus it has zero internal stress.

## What is the meaning of hydrostatic pressure?

Pressure imposed by or existing within a liquid at rest in relation to other bodies. The weight of the water above it, which is equal to the force of gravity acting on its surface area. This force can be expressed as the product of the density of water and its height above some point.

The term "hydrostatic" means relating to water or something that is like water. So, "hydrostatics" is the study of pressures that exist within liquids.

When you lift a bucket of water, you are applying pressure downward on the water. This is called negative pressure or vacuum pressure. As you lift the bucket off the ground, the pressure decreases until the water drops out of the bucket. At that point, there is no longer any pressure on the water; instead, there is only atmospheric pressure surrounding the bucket.

Negative pressures can also be used in medicine to help drain fluid from the body. For example, when your doctor taps on your chest to feel for broken ribs, they are using their hand to create a negative pressure system. This forces blood and fluid out through the openings in the rib cage.

Pressures can be divided into two categories: static and dynamic.

## What is meant by "dynamic pressure"?

The pressure on a surface when a flowing fluid is brought to rest exceeds the pressure on the surface when the fluid is not flowing. This increased pressure occurs because there are more particles from which to collect gas molecules when the fluid is at rest than when it is moving.

Dynamic pressure is the pressure that acts on a body as a result of its movement through the fluid. It is caused by two factors: the force of the fluid on the body, and the body's resistance to this force. The greater the body's resistance, the greater will be the dynamic pressure it creates.

For example, if a person goes swimming in a lake with a strong current, he or she would be subjected to both static and dynamic forces. Because the person is immersed in water, he or she is subject to the force of gravity as well as the force of buoyancy (the upward force due to the weight of the water). However, the person also creates dynamic pressure as he or she moves through the water. The faster the person swims, the greater will be the dynamic pressure he or she creates.

Static pressure is the pressure that acts on a body at rest in a fluid. It is caused only by the weight of the fluid and depends on the depth of the body submerged.

## What is meant by the "pressure of a gas?"?

Pressure is defined as the force exerted by one material on another per unit area. The force that the gas exerts on the container limits is defined as the pressure of the gas. Gas molecules travel in a random pattern along the specified volume. The more collisions there are, the more pressure there is. As long as the container remains intact, the gas will continue to pressurize it.

When you add heat to a system, you increase the movement of particles. This increases the rate at which particles collide with each other and with the container wall. This increases the pressure of the gas.

As soon as the heat input into the system is greater than the heat loss out of the system, then the pressure will start to go up. If the heat input exceeds the heat loss, then the pressure will keep going up until the container ruptures or fills up with gas at some high pressure.

So, pressure is the force per unit area applied by one material on another. It is measured in Pascals (Pa) or N/m2. A very high pressure may cause damage effects, such as explosion or melting, but for most applications a moderate pressure is enough to achieve significant results.

Gas pressures can range from almost zero to thousands of pounds per square inch (PSI). At low temperatures, even a small pressure can cause gases to condense into liquids.

## What do you mean by fluid pressure at a point?

Fluid pressure is the pressure at a place within a fluid caused by the fluid's weight. By dividing the mass of the fluid under examination by the volume of fluid collected, the density of the fluid can be computed. This number is then divided by the depth below sea level or ground level at which the measurement is made, to obtain the local fluid-pressure value.

Fluid pressure at a point is the force per unit area acting on the surface of a vertical slice through that point. If we assume that the fluid is air, then the force on each square centimeter of surface is known as an atmospheric pressure. Since the weight of the fluid is being exerted over a large area, the total pressure at any point is simply the average value of the fluid pressure over an area surrounding that point.

The term "fluid pressure" is also used when referring to the pressure applied to an object submerged in water. This pressure is both upward and downward acting, since water is a viscous fluid and so attempts to flow around objects. The magnitude of this pressure varies with depth below sea level or ground level. At shallow depths the pressure will be high because there is little room for the water to escape, but at greater depths it becomes less severe because there is more space for the water to flow away.

##### Barbara Molleur

Barbara Molleur is an educator with a passion for science. She has been teaching for over 10 years, and has a degree in both Biology and Education.

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