Pressure( P) is a unit of physics to declare force (F) per unit area (A).
Pressure unit often used to measure the strength of a liquid or gas.
Pressure unit can be connected to the unit volume (content) and temperature. The higher pressure in a place with the same content, then the temperature will be higher. It can be used to explain why the temperature in the mountains is lower than in the lowlands, as in the lowlands to higher pressure.
However, this statement is not always true, or except for water vapor, water vapor if the pressure is increased there will be a change of the gas back into liquid. (quoted from wikipedia: condensation). The formula of pressure can also be used to explain why the knives are sharpened and thinned surface becomes sharp. The smaller the surface area, in the same style will get a higher pressure. The air pressure can be measured using a barometer.
Pressure (Pressure) is the force acting normal or perpendicular to a plane. Load on an object in principle form of pressure due to contact of an object with other objects will certainly be an area. Even if a needle will be an enlarged contact area and not a single point.
Review of a balloon that is blown then the air pressure in the balloon continued to be enlarged. If the balloon was blown continuously, the air pressure inside can not be arrested again by the rubber balloon
Hydrostatic pressure is the pressure that occurs under water. This pressure is due to the weight of water that makes the fluid pressure issue. Pressure of a liquid depends on the depth of liquid in a space and gravity also determines the water pressure.
This relationship is formulated as follows: “P = ρgh” where ρ is the fluid densities, g (10 m/s2) is gravity, and h is the depth of the liquid.
The pressure on the liquid (fluid) are generally divided into two kinds of pressure, ie, the pressure on liquid substances that do not move (flow) and pressure fluid that moves (flows).
In this discussion we will focus more pressure on the liquid does not move, or better known by Hydrostatic Pressure. Conceptually Hydrostatic pressure is the pressure prevailing in the fluid on the basis of Pascal’s Law.
Hydrostatic pressure is the pressure exerted by the gravity of the liquid itself is a broad field of press. Assuming that the liquid substance in the form of layers according to the level of the measured depth from the surface of the liquid. Then the hydrostatic pressure of the liquid is equal to every part of the liquid that has the same depth.
Air pressure is the pressure at any point in Earth’s atmosphere. Generally, air pressure is almost equal to the hydrostatic pressure caused by the weight of air above the measurement point. Air masses influenced the general air pressure inside the mass, which creates an area with high pressure (antisiklon) and low pressure (depression). Low pressure areas have less atmospheric mass above its location, where the contrary, a high pressure area has a greater mass of the atmosphere above location.
The atmosphere is a layer that protects the earth. This layer extends to 1000 km into the earth and has a mass of 4.5 x 1018 kg. The mass of the atmosphere that suppresses the surface is called the atmospheric pressure. Atmospheric pressure at sea level is 76 cmHg. Air pressure is measured by the pressure forces on the surface with a particular area, eg 1 cm2. The units used are the atmosphere (atm), millimeters of water column of mercury (mm Hg) or millibars (mbar).
Standard air pressure (sometimes called) normal air pressure) is the pressure of the air column as high as Earth’s upper atmosphere at the latitude of 450 and 00C temperature. amount of air pressure is expressed as 1 atm. A pressure of 1 atm is equivalent to the pressure exerted by a column of mercury as high as 760 mm. pressure units in addition to the atm or mmHg also can and often expressed in units of kg/m2. Conversions between units of air pressure are as follows :1 atm = 760 mmHg = 14.7 Psi = 1.013 mbar. Tool to measure the air pressure is called a barometer. Air pressure decreases with increasing altitude (elevation or altitude).
The relationship between air pressure with altitude was utilized in designing tools for the measurement of altitude is called the altimeter.
Air pressure is affected by temperature
Air pressure is the pressure exerted by the air (because of the weight) to each luas1em plane surface of the earth’s atmosphere up to the limit. distribution of air pressure can be divided into 2:
1. vertical distribution is that the nearer the surface of the earth, the air less dense and more weight. Because was higher than the surface air earth pressure is low.
2. horizontal line in the map shown with Isobars, namely the line connect places with the same air at press same time. air is influenced by factors of factor 1. latitude zones of the earth that shows the air temperature so that the air pressure zone is formed around the equatorial low pressure (doldrum) the cold polar latitudes high lean, middle latitudes (60-70) degrees is a circle of low pressure (subpolar) and latitude (25-35) degree is a zone (zone) of high pressure
Heat Application in Daily Life
Effect of pressure on boiling point, boiling point liquid will rise if the pressure is raised above the surface. Example: Pressure cookers pressure (pressure cooker) to cook the meat more tender quickly, because the water in a pot boiling over 100 ° C or approximately 120 ° C and the pressure to 2 atm. Consequently quick tender meat. Pressure drop on the surface can lower the boiling point, therefore the higher the place above the earth’s surface temperature is lower because the higher the pressure is lower.
Impurity substances can raise the boiling point. Example: sugar water, salt water boiling over 100 ° C, therefore if you cook vegetables using salt meant it was also faster than savory tender. Effect of impurities lower the melting point of substances. Example: Adding salt to the mixture of ice with water to 20 ° C. Because the addition of salt, ice melt below 0 ° C. require heat to melt a substance, heat is taken from the ice itself because there is no supply from the outside. As a result, the ice temperature will drop below 0 ° C even though it was in liquid form.