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Pressure in our everyday lives

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by Jessica Ramgolam on 10 September 2013

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Transcript of Pressure in our everyday lives

Pressure in our everyday lives
Liquid Pressure
The pressure under water increases with how deep you are.

Pressure in liquid is due to the weight of the liquid acting on the surface of any objects in the liquid.
The pressure at any point of a liquid acts equally in all direction.

What is pressure?

Pressure is defined as the force over a given area. Given the same force, the smaller the area of contact, the more pressure is applied. The formula used to describe and calculate pressure is:

Pressure = Force ÷ Area
P = F/A

Air/ Atmospheric Pressure
Liquid Pressure
Vapor Pressure
Surface Pressure
Kinematic Pressure
Stagnation Pressure
Sound Pressure
Partial Pressure
Types of Pressure
Atmospheric conditions
such as high pressure or low pressure, ,medical conditions such as sinus pressure and liquid pressures are all examples of pressure.
These all have a common element: a weight, a pushing, a
Cause of Pressure
Air pressure is the pressure exerted on objects from the air or the Earth's atmosphere. This is the measurement of the weight of the gas above an object on a given surface area. The higher the elevation, the lower the atmospheric pressure exerted because there is less air pressing down on the object.
Air Pressure
The dam is much thicker at the bottom than it is at the top. This is because the pressure of the water is much greater deeper down and the dam needs to be thick at the bottom so that it is strong enough to withstand this larger pressure.
The generator is placed at the lower part so that the pressure of the water is high enough to drive the turbine.
Fluid pressure can be caused by gravity, acceleration, or forces in a closed container. Since a fluid has no definite shape, its pressure applies in all directions.
When you dive to the bottom of a pool, you automatically feel your ears hurting. This occurs because the pressure in a liquid increases as you go further below the surface of the liquid. All the water above you is pressing down on you and squeezing the air inside your ears into a smaller volume.

Pressure Caused by Liquid

P = Pressure
h = depth
ρ = density of liquid
g = Gravitational Field Strength
The cardboard does not fall and the water remains in the glass even though it’s not supported by anything.

The force caused by the atmospheric pressure acts on the surface of the cardboard is greater than the weight of the water in the glass.
Existence of Atmospheric Pressure
Pascal (Pa) is the international standard unit for pressure. The meteorological community uses hecto-Pascal (hPa) as the unit of pressure. It is the same as 1 millibar, a unit of pressure no longer used nowadays.
What is the unit of pressure?
The greatest application of the Bernoulli principle is used in airplanes.
In order for an aircraft to rise into the air, a force must be created that equals or exceeds the force of gravity. This force is called lift. In heavier-than-air craft, lift is created by the flow of air over the wing. The curved shape of the wing causes air to flow faster on top than on bottom. The fast flowing air decreases the surrounding air pressure. As the air pressure is greater below the wing than above, a resulting lift force is created.
The relationship between the velocity and pressure exerted by a moving liquid is described by the Bernoulli's principle: as the velocity of a fluid increases, the pressure exerted by that fluid decreases.
In our Daily Life...
Some handbags have a thin strap. When in contact with the shoulder, it produces high pressure causing our shoulder to feel pain. The smaller the surface area of the handbag strap, the higher the pressure produced. Use the handkerchief that is used to increase the surface area of the thin strap. The larger the surface area of the handbag strap, the lower the pressure produced.
The principle of transmission of fluid-pressure is a principle in fluid mechanics that states that pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure variations (initial differences) remain the same
Hydraulic pumps are used to raise cars in a motor workshop. The machine is equipped with a small cylinder connected to a large cylinder. Both cylinders are filled with oil.
Compressed air is introduced into the small cylinder in which the compressed air exerts a pressure on the surface of the oil.
This pressure is transmitted by the oil to the large cylinder where the pressure acts on a large piston to produce a force which is large enough to lift a car.
Typically we will slowly open turn the cap of the soda bottle, allowing the air to gradually escape before completely removing the lid as to not let it fizz all over the place.The high pressure added into the can by the manufacturers must be held in order for the Carbon Dioxide to remain dissolved. When the bottle is opened, the pressure in the system will drop. The carbon dioxide tends to go back into its gaseous state and leaves in the form of bubbles.
The sharp knife has a very small area of contact with the surface, while the dull knife has a much larger area of contact. If both knives are pushed down with the same force, the sharp knife will exert a much greater pressure on the surface than the dull knife - and pressure cuts.
The downward force that you exert on the ice in either case would be half of your weight.

The shoe distributes the force over a much larger area than the skate does. This means that the skate exerts a much higher pressure on the ice than the shoe does - it is this high pressure that makes ice skating possible!
Camels move faster in sand because it has flat, broad feet which decreases the area of contact. Hence, pressure is reduced.
Pressure is widely used in our daily life. From drinking straws to flying an airplane, we are surrounded by pressure.
When a vacuum cleaner is switched on, it sucks out the air inside the cleaner, causing the pressure inside the cleaner to become low.

The atmospheric pressure which is higher in magnitude, forces the air and dust particles to enter the cleaner.
-When a person sucks through the straw, the pressure in the straw become low.
-The atmospheric pressure outside which is higher will force the water into the straw and consequently into the mouth.
Before pressurized cabins, you couldn't fly much over 10,000 feet high .
Cabin pressurization is used to create a safe and comfortable environment for aircraft passengers and crew flying at high altitude by pumping conditioned air into the cabin. As you go higher in the atmosphere, there is less air pressure. That makes it harder to breathe and leads to a several breathing issues.

Pressurisation of the cabin is achieved by tapping air from the compressor of the engine. This air is passed through heat exchangers before being released into the cabin.
Pressurisation starts from an altitude of about 5000 feet. While the aircraft continues ascending, the cabin pressurisation is maintained at around the same level.
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