How atmospheric pressure affects humans?

1.High altitude are regions on the Earth's surface (or in its atmosphere) that are high above mean sea level. The pressure and temperature of the atmosphere at high altitude is substantially different than at sea level. These differences can affect living organisms, including humans.

2.Low barometric pressure also affects us, if for example we fly in an unpressurized aircraft. At 10,000 ft and above, the air is very thin and the lack of oxygen will affect our mind. Low air pressure can be very unpleasant for humans due to an absence of oxygen, so all areas of aircraft that contain passengers are artificially pressurized.

3.Some studies have also shown that atmospheric pressure can adversely affect human health, though many question whether the small natural variations caused, for example by weather front.

-A weather front is a boundary separating two air mass of different density, and is the principal cause of meteorological phenomenon. In surface weather analysis, fronts are depicted using various colored lines and symbols, depending on the type of fronts, are significant enough to affect humans.

What is the application of athmospheric pressure?

Can-Crushing Experiment
A current U.S. 12 oz soft drink can measures about 6.6 cm(2.6 inches) in diameter and 12.1 cm (4.75 inches) tall. The area of a cylinder of these dimensions is about 316 square cm (49 square inches), including the ends. The force of one athmosphere of pressure on that area is about 3200 newtons (720 lbs). Nevertheless, such cans can be made of very thin aluminum because the same force acts outward from the inside of the can.
If a few cubic centimeters of water is poured into such a can (just enough to cover the bottom) and the can is held above a laboratory burner for about 30 seconds, the water can be brought to the boiling point where its vapor pressure is equal to atmospheric pressure. The vapor will then push most of the air out of the can. If the can is quickly inverted into a beaker of water, sealing off the opening, the sudden drop in vapor pressure will result in enough net inward pressure to quickly crush the can.

Crushing of Steel Drum
Dan Stamm, a physics teacher at Campbell High School in Smyrna, GA constructed a platform for heating water in a steel drum. The drums used had a surface area of about 3000 square inches. The force of one atmosphere of pressure on that area is about 44,000 lbs or 22 tons! Nevertheless, such cans can be made of reasonably thin steel because the same force normally acts outward from the inside of the vessel. The procedure involved pouring about a gallon of water into the drum (just enough to cover the bottom) and and heating it over a propane burner for 15 to 30 minutes. The water is brought to the boiling pointwhere its vapor pressure is equal to atmospheric pressure. The vapor will then push most of the air out of the can. The can is then sealed as the heat is removed. If the drum is cooled quickly, the sudden drop in vapor pressure will result in enough net inward pressure to crush the can.

Savery Engine
This model of the 17th century Savery engine was built by physics teacher Dan Stamm of Campbell High School, Smyrna, GA.
Invented by Thomas Savery in the late 17th century, the Savery engine was the first commercially successful steam engine. It was used to pump water out of mines.
In this model, water is boiled in the metal tank to drive out air, and then when the tank is cooled, it pumps water from the large jug.

Magdeburg Hemispheres
Shown is a small demonstration replica of the original Magdeburg hemisphere. Its diameter is 14 cm (area = 154 sq cm) so that the force of the atmosphere on its cross-sectional area is 1560 Newtons. If a small vacuum pump can remove half of the air, then the force required to pull the hemispheres apart would be about 780 Newtons or 175 pounds.

What is the behavior of gas molecules based on the kinetic theory?

Kinetic Molecular Theory




Basic Concepts



The gas laws developed by Boyle, Charles, and Gay-Lussac are based upon empirical observations and describe the behavior of a gas in macroscopic terms, that is, in terms of properties that a person can directly observe and experience. An alternative approach to understanding the behavior of a gas is to begin with the atomic theory, which states that all substances are composed of a large number of very small particles (molecules or atoms). In principle, the observable properties of gas (pressure, volume, temperature) are the consequence of the actions of the molecules making up the gas.

The Kinetic Molecular Theory of Gases begins with five postulates that describe the behavior of molecules in a gas.

These postulates are based upon some simple, basic scientific notions, but they also involve some simplying assumptions. In reading a postulate, do two things. First, try to understand and appreciate the basic physical idea embodied in the postulate; this idea will ultimately be important in understanding the macroscopic properties of the gas in terms of the behavior the microscopic molecules making up the gas. Second, identify possible weakness or flaws in the postulates. Inaccurate predictions by a theory derive from flawed postulates used in the derivation of the theory.

Postulates
A gas consists of a collection of small particles traveling in straight-line motion and obeying Newton's Laws.
The molecules in a gas occupy no volume (that is, they are points).
Collisions between molecules are perfectly elastic (that is, no energy is gained or lost during the collision).
There are no attractive or repulsive forces between the molecules.
The average kinetic energy of a molecule is 3kT/2. (T is the absolute temperature and k is the Boltzmann constant.)

Behavior of Molecules in a Gas
To illustrate the significance of these postulates, consider the box containing a single molecule shown below. Start the animation and observe the molecule, represented by the blue ball, bouncing and traveling back and forth across the box. The collisions with the walls are perfectly elastic. Energy is neither gained nor lost from the collision. Because the walls do not move, the molecule's speed is unaffected by the collision. The graph plots the particle speed as a function of time. Observe that the speed has a constant value.



Now consider the box below in which several molecules exist. Start the animation and observe the blue molecule. Unlike the system above, this system has multiple molecules and thus collisions between molecules occur. Observe how the speed (and direction) of the molecule changes as a result of a collision. Thus the speed of a given molecule is not constant. From one collision to the next the molecule speeds up, slows down, speeds up, etc.

The graph shows how the speed changes with time. Observe that the speed is a constant in between collisions. At the moment of each collision there is an abrupt change in speed (and in direction).

Averaged over a long period of time, the average kinetic energy of a given molecule is 3kT/2. Similarly, the average kinetic energy of a large number of molecules at a particular instant in time is 3kT/2.

What are the instruments for measuring gas and atmospheric pressure?

Many instruments have been invented to measure pressure.

A manometer could also be referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term manometer is often used to refer specifically to liquid column hydrostatic instruments.

A barometer is an instrument for measuring atmospheric pressure, used especially in weather forecasting.

A McLeod gauge isolates a sample of gas and compresses it in a modified mercury manometer until the pressure is a few mmHg.

Aneroid gauges are based on a metallic pressure sensing element which flexes elastically under the effect of a pressure difference across the element.

A Bourdon gauge uses a coiled tube, which, as it expands due to pressure increase causes a rotation of an arm connected to the tube.

Piston-type gauges counterbalance the pressure of a fluid with a solid weight or a spring.

A vacuum gauge is used to measure the pressure in a vacuum.

Hydrostatic gauges (such as the mercury column manometer) compare pressure to the hydrostatic force per unit area at the base of a column of fluid.

Liquid column gauges consist of a vertical column of liquid in a tube whose ends are exposed to different pressures. The column will rise or fall until its weight is in equilibrium with the pressure differential between the two ends of the tube. A very simple version is a U-shaped tube half-full of liquid.

Sources:

www.answers.com/topic/barometer

en.wikipedia.org/wiki/Pressure_measurement

What are the experiments that show the existance of atmospheric pressure?

EXPERIMENT 1

Pascalís law of transmission of pressure in fluids Pascalís law is a useful application and extension of the phenomena of liquids seeking their levels automatically. Take a vessel that has many limbs and an airtight piston at the centre.

Procedure:

1. Fill the vessel with liquid.

2.Press the piston, you will notice that the liquid level has risen in the other limbs equally. This implies that the pressure applied on the piston is transmitted immediately in other parts of the liquid.

--Remember that an increase in height means increase in pressure. (It is important to note that the liquid has to be a non-compressible fluid. The same will not be applicable to gases.)

Pascalís Law states that pressure exerted at a point in an enclosed (and non-compressible) liquid is transmitted equally in all directions. The pressure is transmitted undiminished.

EXPERIMENT 2

Applications of Pascalís law are plenty. The most common use this has is in hydraulic lifts, car brakes etc. How this is achieved is shown in the diagram below.

Procedure

1. Two cylinders are connected in an airtight fashion.

2. The arrangement is filled with liquid. The piston 1 in one cylinder is smaller than piston 2 in other cylinder.

3. On the smaller piston, a load (force) of W1 is applied.

Now you can appreciate how car breaks function. The break system is filled with special break fluid. A small pressure break paddle is able to stop a moving car which has such a large mass than the break paddle itself!

www.educationalelectronicsusa.com/p/mechs_IV.htm

What is atmospheric pressure?

Atmospheric pressure is sometimes defined as the force per unit area exerted against a surface by the weight of air above that surface at any given point in the Earth's atmosphere.

In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point.

Low pressure areas have less atmospheric mass above their location, whereas high pressure areas have more atmospheric mass above their location.

Similarly, as elevation increases there is less overlying atmospheric mass, so that pressure decreases with increasing elevation.