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Since Trump withdrew from that deal more than a year ago, his administration has reimposed crippling sanctions on Tehran and designated its Revolutionary Guard a foreign terrorist group. Pence said the U. Tensions in the region have risen in recent weeks after oil tankers were attacked near the Strait of Hormuz and Iran downed an unmanned U. The downing of the drone nearly led to a U. Instead, the U. The U. Iran has long maintained it was enriching uranium for peaceful reasons.

While enriched uranium at the 3. Iran has been trying to gain European help in bypassing U. Later Monday, Bolton, the White House national security adviser and a longtime advocate of tough measures against Iran, devoted a large portion of his speech at the same summit to Iran, noting that the that the administration has expanded sanctions to cover metals and the petrochemical sector. Secretary of State Mike Pompeo said the U.

Search News Search web. Story continues. What to Read Next. Pressure in open conditions usually can be approximated as the pressure in "static" or non-moving conditions even in the ocean where there are waves and currents , because the motions create only negligible changes in the pressure. Such conditions conform with principles of fluid statics. The pressure at any given point of a non-moving static fluid is called the hydrostatic pressure.

Closed bodies of fluid are either "static", when the fluid is not moving, or "dynamic", when the fluid can move as in either a pipe or by compressing an air gap in a closed container. The pressure in closed conditions conforms with the principles of fluid dynamics.

The concepts of fluid pressure are predominantly attributed to the discoveries of Blaise Pascal and Daniel Bernoulli. Bernoulli's equation can be used in almost any situation to determine the pressure at any point in a fluid. The equation makes some assumptions about the fluid, such as the fluid being ideal [10] and incompressible.

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While pressures are, in general, positive, there are several situations in which negative pressures may be encountered:. Stagnation pressure is the pressure a fluid exerts when it is forced to stop moving. Consequently, although a fluid moving at higher speed will have a lower static pressure , it may have a higher stagnation pressure when forced to a standstill. Static pressure and stagnation pressure are related by:. The pressure of a moving fluid can be measured using a Pitot tube , or one of its variations such as a Kiel probe or Cobra probe , connected to a manometer.

Depending on where the inlet holes are located on the probe, it can measure static pressures or stagnation pressures. There is a two-dimensional analog of pressure — the lateral force per unit length applied on a line perpendicular to the force. Surface tension is another example of surface pressure, but with a reversed sign, because "tension" is the opposite to "pressure".

In an ideal gas , molecules have no volume and do not interact. According to the ideal gas law , pressure varies linearly with temperature and quantity, and inversely with volume:. Real gases exhibit a more complex dependence on the variables of state. Vapour pressure is the pressure of a vapour in thermodynamic equilibrium with its condensed phases in a closed system. All liquids and solids have a tendency to evaporate into a gaseous form, and all gases have a tendency to condense back to their liquid or solid form. The atmospheric pressure boiling point of a liquid also known as the normal boiling point is the temperature at which the vapor pressure equals the ambient atmospheric pressure.

With any incremental increase in that temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure and lift the liquid to form vapour bubbles inside the bulk of the substance. Bubble formation deeper in the liquid requires a higher pressure, and therefore higher temperature, because the fluid pressure increases above the atmospheric pressure as the depth increases. The vapor pressure that a single component in a mixture contributes to the total pressure in the system is called partial vapor pressure.

When a person swims under the water, water pressure is felt acting on the person's eardrums. The deeper that person swims, the greater the pressure. The pressure felt is due to the weight of the water above the person. As someone swims deeper, there is more water above the person and therefore greater pressure.

Pressure Synonyms, Pressure Antonyms |

The pressure a liquid exerts depends on its depth. Liquid pressure also depends on the density of the liquid. If someone was submerged in a liquid more dense than water, the pressure would be correspondingly greater. The pressure due to a liquid in liquid columns of constant density or at a depth within a substance is represented by the following formula:. With the "area" in the numerator and the "area" in the denominator canceling each other out, we are left with. The pressure a liquid exerts against the sides and bottom of a container depends on the density and the depth of the liquid.

If atmospheric pressure is neglected, liquid pressure against the bottom is twice as great at twice the depth; at three times the depth, the liquid pressure is threefold; etc. Or, if the liquid is two or three times as dense, the liquid pressure is correspondingly two or three times as great for any given depth. Liquids are practically incompressible — that is, their volume can hardly be changed by pressure water volume decreases by only 50 millionths of its original volume for each atmospheric increase in pressure.

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Thus, except for small changes produced by temperature, the density of a particular liquid is practically the same at all depths. Atmospheric pressure pressing on the surface of a liquid must be taken into account when trying to discover the total pressure acting on a liquid. When this distinction is important, the term total pressure is used. Otherwise, discussions of liquid pressure refer to pressure without regard to the normally ever-present atmospheric pressure. It is important to recognize that the pressure does not depend on the amount of liquid present.

Volume is not the important factor — depth is. The average water pressure acting against a dam depends on the average depth of the water and not on the volume of water held back. If four vases contain different amounts of water but are all filled to equal depths, then a fish with its head dunked a few centimetres under the surface will be acted on by water pressure that is the same in any of the vases. If the fish swims a few centimetres deeper, the pressure on the fish will increase with depth and be the same no matter which vase the fish is in.

If the fish swims to the bottom, the pressure will be greater, but it makes no difference what vase it is in. All vases are filled to equal depths, so the water pressure is the same at the bottom of each vase, regardless of its shape or volume. If water pressure at the bottom of a vase were greater than water pressure at the bottom of a neighboring vase, the greater pressure would force water sideways and then up the narrower vase to a higher level until the pressures at the bottom were equalized.

Pressure is depth dependent, not volume dependent, so there is a reason that water seeks its own level. Restating this as energy equation, the energy per unit volume in an ideal, incompressible liquid is constant throughout its vessel. At the surface, gravitational potential energy is large but liquid pressure energy is low. At the bottom of the vessel, all the gravitational potential energy is converted to pressure energy.


The sum of pressure energy and gravitational potential energy per unit volume is constant throughout the volume of the fluid and the two energy components change linearly with the depth. An experimentally determined fact about liquid pressure is that it is exerted equally in all directions. Because a liquid can flow, this pressure isn't only downward.

Pressure is seen acting sideways when water spurts sideways from a leak in the side of an upright can. Pressure also acts upward, as demonstrated when someone tries to push a beach ball beneath the surface of the water. The bottom of a boat is pushed upward by water pressure buoyancy. When a liquid presses against a surface, there is a net force that is perpendicular to the surface.

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Although pressure doesn't have a specific direction, force does. A submerged triangular block has water forced against each point from many directions, but components of the force that are not perpendicular to the surface cancel each other out, leaving only a net perpendicular point. Then it curves downward due to gravity.

If there are three holes in a bucket top, bottom, and middle , then the force vectors perpendicular to the inner container surface will increase with increasing depth — that is, a greater pressure at the bottom makes it so that the bottom hole will shoot water out the farthest. The force exerted by a fluid on a smooth surface is always at right angles to the surface. From Wikipedia, the free encyclopedia. This article is about pressure in the physical sciences. For other uses, see Pressure disambiguation. Force distributed continuously over an area. The classical Carnot heat engine.

Classical Statistical Chemical Quantum thermodynamics. Zeroth First Second Third. System properties.

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  • Note: Conjugate variables in italics. Work Heat. Material properties. Carnot's theorem Clausius theorem Fundamental relation Ideal gas law. Free energy Free entropy. History Culture. History General Entropy Gas laws. Entropy and time Entropy and life Brownian ratchet Maxwell's demon Heat death paradox Loschmidt's paradox Synergetics.

    Caloric theory Theory of heat. Heat ". Thermodynamics Heat engines. Main article: Ideal gas law. Main article: Vapour pressure. Solid mechanics. Fluid mechanics. Surface tension Capillary action. Further, both spellings are often used within a particular industry or country. Industries in British English-speaking countries typically use the "gauge" spelling. Physics: principles with applications. Upper Saddle River, N. Compendium of Chemical Terminology, 2nd ed. Oxford: Blackwell Scientific Publications. Archived from the original on Retrieved US Navy Diving Manual, 6th revision.

    Archived PDF from the original on Astrophysics and Space Science.