Atmospheric Pressure

"Atmospheric pressure is the pressure at any 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.".There is less atmospheric mas above low pressure areas, and high have more atmospheric mass above them. When elevation increases there is less atmospheric mass, so pressure decreases with the increase of elevation. "A column of air 1 square inch in cross section, measured from sea level to the top of the atmosphere, would weigh approximately 14.7 lbf. A 1 m² (11 sq ft) column of air would weigh about 100 kilonewtons (equivalent to a mass of 10.2 tonnes at the surface)." A unit of pressureis defined s being the equal to 101.325 kPa."The standard atmosphere (symbol: atm)"

resource:http://en.wikipedia.org/wiki/Atmospheric_pressure

vapor pressure

"Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases (i.e., liquid or solid)." Vapor pressure also a term used to describe the tendancy a liquid has to evaporate; it measures the tendancy of molecules and atoms to escape froma liquid or solid." A liquid's atmospheric pressure boiling point corresponds to the temperature at which its vapor pressure is equal to the surrounding atmospheric pressure and it is often called the normal boiling point." "The higher is the vapor pressure of a liquid at a given temperature, the lower is the normal boiling point of the liquid." The liquids with the highest vapor pressures have the lowest boiling points."For example, at any given temperature, propane has the highest vapor pressure of any of the liquids in the chart. It also has the lowest normal boiling point(-43.7 °C), which is where the vapor pressure curve of propane (the purple line) intersects the horizontal pressure line of one atmosphere (atm) of absolute vapor pressure."




refrence:http://en.wikipedia.org/wiki/Vapor_pressure#Units_of_vapor_pressure

Blood pressure

Blod pressure is the force that causes the blood to circulate on the walls of blood vessels. As the blood moves through the arteries and veins, it decreases. Blood pressure can be measured by sphygmomanometer, and it uses a coulumn of mecury to reflect the circulating pressure."The average pressure throughout the cardiac cycle is reported as mean blood pressure(arterial pressure); the pulse pressure reflects the difference between the maximum and minimum pressures measured."
"All levels of arterial pressure put mechanical stress on the arterial walls." High blood pressure increases the work of the heart and progresion of unhealthy tissue growth. The higher the pressure, the higher the stress that is presen. Then the heart muscles tend to thicker enlarge and become weak;over time. High blood pressure is also the result of stroke, heart attacks and heart failure. Blood pressure that is too low is known as hypotension. Low blood pressure is a sign of severe disease;the perfusion of the brainbecomes critically decreased, causing lightheadedness, weakness and fainting.



Refrence:http://en.wikipedia.org/wiki/Blood_pressure#High_arterial_pressure

Peer pressure

"Peer pressure is a term describing the pressure exerted by a peer group
in encouraging a person to change their attitude, behavior and/or morals, to conform to, for example, the
group's actions, fashion sense, taste in music and television, or outlook on
life."(wikipedia.com)
If you were a teenager you probably went through peer pressure, we all go through it. If you wanted to hang out with a certain group you needed to have or do certain things. When your being pressured by your peers, its usually about shoplifting, drinking, drugs, smoking, doing risky things while driving or having sex before your ready. You might refuse, they will just try to get you to do it any way, by saying things such as: "are you chicken", "your not hurting anyone", "i wont be your friend if you don't do it" and other stuff. You should never give into peer pressure but all too often we do and then regret it.
For example, an article I found at:http://www.kidshealth.org/teen/your_mind/relationships/peer_pressure.html

"Now!" whispered Suki. "Quick, while the clerk's not looking."

Heart pounding, Leah leaned against the store's unattended makeup display and slid two tubes of lipstick into her purse. She looked bored and detached as she followed her friends Suki and Jill out of the store, but inside she felt panicked.

"I can't believe you made me do that," Leah wailed.

"Relax," said Jill. "Everybody does it sometimes. And we didn't make you do it."

She said nothing, but Leah knew she wouldn't have done that on her own.

Not all peer pressure is bad! The good kind of peer pressure is refereed to as peer influence.
Our friends play and important part in our life, we might find someone with the same likes and dislikes and you, and if you have peers dedicated to doing good in school they set a good examples for you, you friends also pay attention to your problems and give you advice and they will quickly tell you if they think your doing something bad or risky.

What is pressure?

Pressure, pronounciation:\ˈpre-shər\
Function: noun
Etymology: Middle English, from Anglo-French, from Late Latin pressura, from Latin, action of pressing, pressure, from pressus, past participle of premere
Definitions:
1 a: the burden of physical or mental distress b: the constraint of circumstance : the weight of social or economic imposition
2: the application of force to something by something else in direct contact with it : compression
3archaic : impression, stamp
4 a: the action of a force against an opposing force b: the force or thrust exerted over a surface divided by its area c: electromotive force
5: the stress or urgency of matters demanding attention : exigency
6: the force of selection that results from one or more agents and tends to reduce a population of organisms
7: the pressure exerted in every direction by the weight of the atmosphere
8: a sensation aroused by moderate compression of a body part or surface

(sources:http://www.merriam-webster.com/dictionary)