Hydraulic brakes

Many cars have anti-lock braking systems (ABS) to prevent the frictional force of the brakes from locking the wheels, causing the car to skid. In an anti-lock braking system, a sensor controls the rotation of the car's wheels when the brakes come on. If a wheel is about to lock, the sensors detect that the rotation speed is dropping suddenly, and they reduce the brake pressure for an instant to prevent it from locking. Compared to traditional braking systems, anti-lock braking systems allow the driver to control the car more effectively in these situations, especially if the road is wet or covered in snow.

Refrigeration

Refrigeration is based on the alternative application of high and low pressure, circulating a fluid at times of pressure through a pipe. When the fluid goes from high to low pressure in the evaporator, the fluid cools and removes heat inside the refrigerator.

The fluid is in a closed circuit, which begins in the compressor. It is there where the refrigerant fluid, in a gaseous state, is compressed at high pressure and high temperature; Then, through a pipe, it is sent to the condenser where, maintaining the pressure, it will be cooled in such a way that it will go from a gaseous state to a liquid state. Once this process is completed, the liquid fluid will be directed through another pipe to the evaporator, where through a throttle valve - which can be a capillary pipe, a thermostatic expansion valve (TEV) or another - after which the liquid is "released" to a low pressure environment (such as the evaporator), producing the violent evaporation of the liquid for which the necessary heat is transferred, generating the "cooling" of the environment located around the pipe and consequently of the products to refrigerate. The gas then returns to the compressor through the return line (pipe), completing the compression refrigeration circuit.

Car tires

They are inflated to a pressure of 206,842 Pa "Pascal (unit)"), which is equivalent to 30 psi (using psi as the unit of pressure relative to atmospheric pressure). This is done so that the tires have elasticity in the event of strong impacts (very common when driving in the car). The air is trapped at a higher pressure than atmospheric pressure inside the chambers (approximately 2 times higher), and in the most modern tires between the flexible rubber cover and the rim, which is made of rigid metal.

The pressure that originates on the free surface of liquids contained in capillary tubes, or in liquid droplets, is called their capillary pressure.

It occurs due to surface tension. In a drop it is inversely proportional to its radius "Radius (geometry)"), reaching considerable values.

For example, in a drop of mercury one ten-thousandth of a millimeter in diameter there is a capillary pressure of 100 atmospheres. Hydrostatic pressure corresponds to the quotient between the normal force (F) that acts, within a fluid, on one face of a body and that is independent of its orientation.

It depends only on the depth at which the considered element is located.

That of a vapor, which is in dynamic equilibrium with a solid or liquid at any temperature and which depends only on said temperature and not on the volume, is designated by the name vapor pressure or saturation.

While pressures are generally positive, there are several situations in which negative pressures can be found:.

• - When it comes to relative pressures (gauge). For example, an absolute pressure of 80 kPa can be described as a gauge pressure of −21 kPa (e.g., 21 kPa below an atmospheric pressure of 101 kPa). For example, abdominal decompression") is an obstetric procedure during which negative gauge pressure is applied intermittently to the abdomen of a pregnant woman.

• - Negative absolute pressures are possible. They are effectively tensions&action=edit&redlink=1 "Stress (physics) (not yet written)"), and both bulk solids and bulk liquids can be subjected to negative absolute pressure by pulling on them.[6]​ Microscopically, molecules in solids and liquids have attractive interactions that dominate the thermal kinetic energy, so some tension can be maintained. Thermodynamically, however, a bulk material under negative pressure is in a metastable state, and is especially fragile in the case of liquids where the negative pressure state is similar to overheating and is easily susceptible to cavitation.[7]​ In certain situations, cavitation can be avoided and negative pressures are maintained indefinitely,[7]​ for example, liquid mercury has been observed to hold up to −425 atm in glass containers. clean.[8]​ It is believed that negative liquid pressures are involved in the rise of sap") in plants greater than 10 m (the atmospheric pressure head") of the water).[9]​.

• - The Casimir effect can create a small force of attraction due to interactions with vacuum energy; This force is sometimes called "vacuum pressure" (not to be confused with the negative "gauge pressure" of a vacuum).

• - For non-isotropic stresses in rigid bodies, depending on how the orientation of a surface is chosen, the same force distribution can have a positive pressure component along one normal&action=edit&redlink=1 "Surface normal (geometry) (not yet written)"), with a negative pressure component acting along another surface normal.

• The tensions in an electromagnetic field are generally not isotropic, with the pressure normal to a surface element (the normal voltage) being negative and positive for surface elements perpendicular to it.

• - In cosmology, dark energy creates a very small but cosmically significant amount of negative pressure, which accelerates the expansion of the universe.

The average atmospheric pressure is 101,325 pascals (101.3 kPa)[10]​ at sea level, where 1 atm = 1.01325 bar = 101,325 Pa = 1.033 kgf/cm² and 1 mca = 9.81 kPa.

Obsolete manometric units of pressure, such as the millimeter of mercury (still used in medicine),[11]​ are based on the pressure exerted by the weight of some reference fluid under a certain standard gravity. Millimeters of water column are also used.

• - Unidades de presión.

• - Isobara.

• - Conversión de unidades.

Physical quantities

• - Vapor pressure.

• - Critical pressure.

• - Partial pressure.

• - Atmospheric pressure.

• - Gauge pressure.

• - Dynamic pressure.

• - Static pressure.

• - Pressure in a fluid.

• - Radiation pressure.

• - Sound pressure.

• - Empty.

Medicine

• - Blood pressure.

• - Intraocular pressure.

• - Wikimedia Commons hosts a multimedia category on Pressure.

• - Wiktionary has definitions and other information about pressure.

Hydraulic brakes

Many cars have anti-lock braking systems (ABS) to prevent the frictional force of the brakes from locking the wheels, causing the car to skid. In an anti-lock braking system, a sensor controls the rotation of the car's wheels when the brakes come on. If a wheel is about to lock, the sensors detect that the rotation speed is dropping suddenly, and they reduce the brake pressure for an instant to prevent it from locking. Compared to traditional braking systems, anti-lock braking systems allow the driver to control the car more effectively in these situations, especially if the road is wet or covered in snow.

Refrigeration

Refrigeration is based on the alternative application of high and low pressure, circulating a fluid at times of pressure through a pipe. When the fluid goes from high to low pressure in the evaporator, the fluid cools and removes heat inside the refrigerator.

The fluid is in a closed circuit, which begins in the compressor. It is there where the refrigerant fluid, in a gaseous state, is compressed at high pressure and high temperature; Then, through a pipe, it is sent to the condenser where, maintaining the pressure, it will be cooled in such a way that it will go from a gaseous state to a liquid state. Once this process is completed, the liquid fluid will be directed through another pipe to the evaporator, where through a throttle valve - which can be a capillary pipe, a thermostatic expansion valve (TEV) or another - after which the liquid is "released" to a low pressure environment (such as the evaporator), producing the violent evaporation of the liquid for which the necessary heat is transferred, generating the "cooling" of the environment located around the pipe and consequently of the products to refrigerate. The gas then returns to the compressor through the return line (pipe), completing the compression refrigeration circuit.

Car tires

They are inflated to a pressure of 206,842 Pa "Pascal (unit)"), which is equivalent to 30 psi (using psi as the unit of pressure relative to atmospheric pressure). This is done so that the tires have elasticity in the event of strong impacts (very common when driving in the car). The air is trapped at a higher pressure than atmospheric pressure inside the chambers (approximately 2 times higher), and in the most modern tires between the flexible rubber cover and the rim, which is made of rigid metal.

The pressure that originates on the free surface of liquids contained in capillary tubes, or in liquid droplets, is called their capillary pressure.

It occurs due to surface tension. In a drop it is inversely proportional to its radius "Radius (geometry)"), reaching considerable values.

For example, in a drop of mercury one ten-thousandth of a millimeter in diameter there is a capillary pressure of 100 atmospheres. Hydrostatic pressure corresponds to the quotient between the normal force (F) that acts, within a fluid, on one face of a body and that is independent of its orientation.

It depends only on the depth at which the considered element is located.

That of a vapor, which is in dynamic equilibrium with a solid or liquid at any temperature and which depends only on said temperature and not on the volume, is designated by the name vapor pressure or saturation.

While pressures are generally positive, there are several situations in which negative pressures can be found:.

• - When it comes to relative pressures (gauge). For example, an absolute pressure of 80 kPa can be described as a gauge pressure of −21 kPa (e.g., 21 kPa below an atmospheric pressure of 101 kPa). For example, abdominal decompression") is an obstetric procedure during which negative gauge pressure is applied intermittently to the abdomen of a pregnant woman.

• - Negative absolute pressures are possible. They are effectively tensions&action=edit&redlink=1 "Stress (physics) (not yet written)"), and both bulk solids and bulk liquids can be subjected to negative absolute pressure by pulling on them.[6]​ Microscopically, molecules in solids and liquids have attractive interactions that dominate the thermal kinetic energy, so some tension can be maintained. Thermodynamically, however, a bulk material under negative pressure is in a metastable state, and is especially fragile in the case of liquids where the negative pressure state is similar to overheating and is easily susceptible to cavitation.[7]​ In certain situations, cavitation can be avoided and negative pressures are maintained indefinitely,[7]​ for example, liquid mercury has been observed to hold up to −425 atm in glass containers. clean.[8]​ It is believed that negative liquid pressures are involved in the rise of sap") in plants greater than 10 m (the atmospheric pressure head") of the water).[9]​.

• - The Casimir effect can create a small force of attraction due to interactions with vacuum energy; This force is sometimes called "vacuum pressure" (not to be confused with the negative "gauge pressure" of a vacuum).

• - For non-isotropic stresses in rigid bodies, depending on how the orientation of a surface is chosen, the same force distribution can have a positive pressure component along one normal&action=edit&redlink=1 "Surface normal (geometry) (not yet written)"), with a negative pressure component acting along another surface normal.

• The tensions in an electromagnetic field are generally not isotropic, with the pressure normal to a surface element (the normal voltage) being negative and positive for surface elements perpendicular to it.

• - In cosmology, dark energy creates a very small but cosmically significant amount of negative pressure, which accelerates the expansion of the universe.

The average atmospheric pressure is 101,325 pascals (101.3 kPa)[10]​ at sea level, where 1 atm = 1.01325 bar = 101,325 Pa = 1.033 kgf/cm² and 1 mca = 9.81 kPa.

Obsolete manometric units of pressure, such as the millimeter of mercury (still used in medicine),[11]​ are based on the pressure exerted by the weight of some reference fluid under a certain standard gravity. Millimeters of water column are also used.

• - Unidades de presión.

• - Isobara.

• - Conversión de unidades.

Physical quantities

• - Vapor pressure.

• - Critical pressure.

• - Partial pressure.

• - Atmospheric pressure.

• - Gauge pressure.

• - Dynamic pressure.

• - Static pressure.

• - Pressure in a fluid.

• - Radiation pressure.

• - Sound pressure.

• - Empty.

Medicine

• - Blood pressure.

• - Intraocular pressure.

• - Wikimedia Commons hosts a multimedia category on Pressure.

• - Wiktionary has definitions and other information about pressure.