Hello and welcome to TranslatorsCafe.com channel. In this video we will talk about pressure.
We will discuss the units for measuring pressure; also we will talk about atmospheric pressure
and how it is used in everyday life and in technology. We will also talk about pressure
inside our body and in space travel. We will also talk about the role of pressure in the
formation of hydrocarbons and diamonds. Finally, will discuss some interesting applications
of pressure.
Pressure is defined as force per unit of area. If the same force is applied to two areas,
a smaller and a larger one, the pressure would be greater for the smaller area.
I am sure you will agree that it is less scary to be stepped on by someone wearing running
shoes than by someone wearing stilettos. We can also demonstrate this principle in
action when using a knife. If we try pushing a sharp knife down through a carrot or a tomato,
we will cut it. The area where the force is applied is small,
so the pressure is high enough to cut through the carrot.
Now let's try to use roughly the same force but with the blunt end of the knife. You can
see that we cannot cut through carrot because the area is greater and the pressure is lower
as a result. Pressure is everywhere, and we use it in everyday
life, in the industry, and in technology. Let's take this spray paint bottle, for example.
The paint inside it is under pressure, and this is why it is sprayed out, when we press
the dispenser button. Now let's look at a simple experiment with
using atmospheric pressure. Let's pour some water into a glass and cover it with a piece
of cardboard. While carefully holding the cardboard against the rim of the glass, let's
turn it upside down. Now, let's carefully release the cardboard.
As you can see, it stays in place even though we are not holding it, and the water does
not escape the glass. This is due to the atmospheric pressure, acting upon the cardboard. We can
also conduct this experiment using a sheet of paper instead of the cardboard.
The SI unit for pressure is the pascal, which is newton per square meter.
In some cases pressure of gases is measured as the difference between the total or absolute
pressure and the atmospheric pressure. This is known as gauge pressure, and it is the
pressure measured when determining the air pressure in car tires.
Measuring devices often show gauge pressure, although absolute pressure sensors are also
in use.
Atmospheric or air pressure is the pressure
of air in a given environment. It usually refers to the weight of the column of atmospheric
air above the unit of surface area. Atmospheric pressure affects weather and temperature.
Considerable changes in the atmospheric pressure cause discomfort for people and animals.
Decrease in atmospheric pressure can cause psychological and physical discomfort for
people and animals, or even death. For this reason, airplane cabins, which would otherwise
experience low air pressure at cruising heights, are artificially pressurized.
Atmospheric pressure decreases with the increase in altitude. People and animals, who live
at high altitudes, for example in the Himalayas, adapt to the low pressure. Travelers, on the
other hand, often need to take precautionary measures to avoid discomfort.
Some people, such as mountaineers, are affected by altitude sickness, caused by the oxygen
deficiency in the blood. This condition can become chronic with prolonged exposure.
In severe cases people may have life-threatening symptoms and be affected by high altitude
cerebral or pulmonary edema. Risk of severe altitude sickness typically increases at altitudes
above 2,400 meters. To prevent altitude-related health problems,
medical professionals recommend avoiding depressants such as alcohol and sleeping pills, to hydrate
well, and to ascend to higher altitudes at a slow pace, for example on foot, instead
of using transportation. Additional recommendations include diet high
in carbohydrates, and also resting well, especially for individuals who ascended quickly.
This will allow the body to combat the oxygen shortage, which results from low atmospheric
pressure. Following the recommendations that I mentioned
will help your body to produce more red blood cells that will carry oxygen to the brain
and the internal organs. Your heart and respiratory rates will also increase, among other adaptations.
Emergency treatment for severe altitude sickness has to be provided immediately. It is paramount
to bring the patient to lower altitudes where the pressure is higher, preferably to the
altitude below 2400 meters above the sea level. Treatment also includes medication, and use
of the Gamow Bag. The Gamow Bag is a portable light-weight container
that can be pressurized by using a foot pump. The patient is put inside the bag to simulate
lower altitudes. This is an emergency treatment and simply using the Gamow Bag is not enough.
The patient still needs to be transported to lower altitudes.
Astronauts and pilots who have to work at high altitudes use pressure suits to compensate
for the low air pressure. Full-pressure suits are used in space. They
protect the entire body of the astronaut from the low pressure in the environment. Partial-pressure
suits provide counter-pressure and assist with breathing at high altitude. They are
used by pilots.
Hydrostatic pressure is the pressure of fluid
caused by the force of gravity. It is an important factor not only in engineering and physics,
but also in medicine. For example, blood pressure is the hydrostatic pressure of blood on the
blood vessel walls. It usually refers to arterial pressure. It
is represented by two numbers: systolic or maximum pressure and diastolic or minimum
pressure during a heartbeat. The instrument used to measure blood pressure
is called a sphygmomanometer. Millimeters of mercury are used as units for blood pressure
measurements, even in countries like the USA and the UK, where inches are used for measuring
length.
A Pythagorean cup is an interesting device,
which uses the principles of hydrostatic pressure. According to legend, it was designed by Pythagoras
to moderate wine drinking. Other sources mention that this cup was meant to regulate the drinking
of water during a drought. It usually has a stem and always has a dome
inside of it, which allows liquid to enter from the bottom through the embedded pipe.
This pipe runs from the bottom of the stem of the cup to the top of the dome, then it
bends, and opens into the cup. Liquid enters the pipe through this opening. The other side
of the pipe that runs through the stem also has an opening at the bottom of the stem.
The design and operating principles of a Pythagorean cup are similar to the ones in modern toilet
bowls. If the liquid that fills the cup is above
the top of the pipe, then it spills through the bottom of the cup, due to hydrostatic
pressure. If the liquid is below that level, one can use the cup in a conventional way.
Pressure is a critical element in geology. Formation of gemstones requires pressure,
both for the natural and for the laboratory-made synthetic gemstones.
Crude oil and gas are also formed by intense pressure and heat from remnants of plants
and animals. In contrast to gemstones, which mostly form in rock formations, oil is generally
formed in the beds of water such as in rivers and seas. There, organic material is covered
with sand and silt, which gradually accumulates above it.
The weight of the sand and water above exert pressure. With time, these materials are buried
deeper and deeper and reach several kilometers below the surface of the Earth.
Because the temperature increases by about 25 °C per each kilometer below the surface,
it reaches 50 to 80 °C at these depths. Depending on the total temperature and temperature fluctuation,
gas may be created instead of oil.
The process of gemstone formation varies,
but often pressure is an important factor. Diamonds, for example, are created in the
mantle of the Earth, in the condition of intense pressure and temperature.
They then emerge on or near the surface during volcanic eruptions, when magma carries them
up. Some diamonds come to Earth inside meteorites, and scientists speculate that their formation
on other planets is similar to Earth.
Synthetic gemstone industry on the industrial
scale started in the 1950s, and it is currently expanding. Some consumers still prefer mined
gemstones, but there is a shift in consumer preferences, especially because of the many
problems with gemstone mining that came to light recently.
One of the methods used for growing diamonds in the laboratory is the high pressure high
temperature method also known as HPHT. In this method carbon is subjected to high
temperature over 1000 °C and pressure of about 5 GPa. Generally, diamond seeds are
used as a base and graphite is a high-purity carbon source from which the new diamond grows.
This method is common, especially for making gemstones, because it is cheap compared to
the alternative methods. These laboratory-grown diamonds have similar and sometimes superior
properties to the naturally-formed diamonds, depending on the manufacturing method.
Unlike natural diamonds, which are more commonly clear, man-made diamonds are often colored.
Diamonds are widely used for industrial purposes due to their properties, especially hardness.
Optical qualities, as well as heat conductivity and resistance to alkalis and acids are also
valued. Cutting tools use diamond coating, and diamond
powder is included in abrasive materials. Currently a large portion of industrial diamonds
is made in the laboratories because synthetic production is cheaper than mining, and also
because the demand for industrial diamonds cannot be met through mining exclusively.
The high pressure high temperature process is mainly used when working with synthetic
diamonds. However, it is now also used on natural diamonds to enhance or adjust their
color properties. Presses of different design can be used in
the process. Cubic-type presses are the most expensive and complicated. They are mainly
used for enhancing or changing colors in the natural diamonds. The growth within the capsule
of the press is about 0.5 carats of rough diamond per day.
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