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# Pressure

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## Popescu Mihai

on 31 January 2013

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#### Transcript of Pressure

Pressure What Pressure is... We will talk about.. Why is it important... What does it have to do with physics... And most importantly... Why it is such an awesome Topic. What is Pressure? Pressure (the symbol: p) is the ratio of force to the area over which that force is distributed. in other words... pressure is force per unit area applied in a direction perpendicular to the surface of an object. Mathematically speaking... P= F A _ where... P=PRESSURE F=NORMAL FORCE A=AREA OF THE SURFACE ON CONTACT For liquids the formula is P=pgh (but more on that later) Pressure is a scalar quantity. It relates the vector surface element (a vector normal to the surface) with the normal force acting on it. Now, why is Pressure so Important? We experiment Pressure in our daily life... Let's start off with some cool examples. Pressure in Fluids Fluid pressure is the pressure at some point within a fluid, such as water or air. Fluid pressure occurs in one of two situations: A) an open condition, called "open channel flow" -The Ocean
-A Swimming Pool
-The Atmosphere. Example: OR B) a closed condition, called "closed conduits" Example: -Water line
-Gas line. But where does this bring us? Types of pressure Water pressure escalates with depth. The water pressure at the bottom of a lake is equal to the weight of the column of water above divided by the area of that column. Water Pressure Pressure at depth is Weight / Area Atmospheric pressure Atmospheric pressure is the force per unit area exerted on a surface by the weight of air above that surface in the atmosphere of Earth. The mean sea level pressure (MSLP) is the atmospheric pressure at sea level. 15 year average mean sea level pressure for June
July
August (top) December
January
February (bottom) Physics part of pressure Brief introduction to the biological part! Ever heard of the saying: "I'm under a lot of pressure recently...!" What does that mean? Whenever we experience stressful events in our lives, we sometimes get headaches. There are two types of headaches. Primary: caused by health issues that we are born with or come across. Secondary: caused by environmental states, such as cold weather, atmospheric pressure, dehydration etc.. Headaches usually deliver this negative sensation named pressure when we try to sit up from the bed or a chair. without even knowing it... Now let's understand what this means. Let's use a more cleaner world map. The study of pressure over the course of 15 years shows that: The highest changes in pressure in the course of December, January, and February were in RUSSIA Followed by the highest changes in June, July and August, which were scattered randomly all over the world. Welcome to the FirSTep Lumina Physics Contest! Pressure is all around us! The pressure inside the tires of our bikes! The pressure inside our tires from our bikes can reach pressure levels from 35psi - 135psi 135 being in special conditions, like a race track. Thumbtack exercise! Put your finger on one wall and try to apply force to it. Now, normally if you're not some kind of super hero, you wont be able to affect the wall, damage-wise. Try it again, only this time use a thumbtack, and you will see that the
wall is easily scratchable. This happens due to the force that applies itself only on a smaller area... The head of the thumbtack! Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. Blood Pressure The blood pressure in the circulation is principally due to the pumping action of the heart. Pressure underwater As you go deeper into the ocean, the pressure starts to accumulate to the point of being inhabitable. Certain fish have the capability to
withstand so much pressure, and so they
live on the bottom of the ocean. It truly is. Let's end this with some happy thoughts! Which brings us to our last part of the lesson! The Chemical part of Pressure You may be wondering what Chemestry has to do with Pressure? Sure, it is a physics topic. It is found in our body and helps us sustain ourselves, understandable. We use it in Technology to make our lives easier. The answer may surprise you! The biggest application of pressure in chemistry is mostly reactions of certain combinations of elements. But by far, the most interesting application of pressure in chemistry is the IDEAL GAS THEORY An ideal gas is a theoretical gas composed of a set of randomly moving, non-interacting point particles. One can visualize it as a collection of perfectly hard spheres which collide but which otherwise do not interact with each other. Such a gas does not exist!
But it sure is cool to think about it! So you see. Pressure is every where.. In Physics Biology Chemistry I hope you have enjoyed watching this project as much as I did making it! Popescu Mihai Class 9A
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