Pressure The force exerted

Liquid pressure The force exerted by a liquid on per unit area determined by the formula of p = h-d... 

Pressure The force exerted over a unit area. 

Kilo bar—unit of measure used to express the high pressures found within Earth s interior. It is referenced to air pressure, the force exerted by the weight of the atmosphere at Earth s surface, which equals one bar. A kilobar is 1000 bars. 

Pressure. The force exerted per unit area of a fluid, often designated as pounds per square inch (psi). 

Pressure—The force exerted against an opposing fluid or thrust distributed over a surface. 

Gas pressure The force exerted by a gas in its surroundings. In the United States, gas pressure is commonly designated in pounds per square inch (psi). The analogous SI unit is the kilopascal (kPa). One psi equals 6.894757 kPa. The term psia refers to absolute pressure. Absolute pressure is based on a zero reference point, the perfect vacuum. Measured from this reference, the standard atmospheric pressure at sea level is 14.696 psi however, local atmospheric pressure may deviate from this standard value because of weather conditions and distance above or below sea level. Gauge pressure, designated by the term psig, is that pressure above local atmospheric pressure. Therefore, psia minus local atmospheric pressure equals psig. 

Pressure the force exerted per unit area of surface. (5.1) Primary alcohol an alcohol in which the hydroxyl group is attached to a carbon atom that is itself bonded to only one other carbon atom. (24.6)... 

It is important to estabhsh the link between buoyancy force and hydrostatic pressure. The forces exerted by the movement of a fluid on an object contained in that fluid are in most cases calculated using pressure p, which is the difference between the absolute and hydrostatic pressures (equation [1.34]). The force calculated by integrating the pressiue field, p, across the surface of the object is the one produced... 

The chemistry of cement slurries is complex. Additives will be used to ensure the slurry remains pumpable long enough at the prevailing downhole pressures and temperatures but sets (hardens) quickly enough to avoid unnecessary delays in the drilling of the next hole section. The cement also has to attain sufficient compressive strength to withstand the forces exerted by the formation over time. A spacer fluid is often pumped ahead of the slurry to clean the borehole of mudcake and thereby achieve a better cement bond between formation and cement. 

Pressure. Standard atmospheric pressure is defined to be the force exerted by a column of mercury 760-mm high at 0°C. This corresponds to 0.101325 MPa (14.695 psi). Reference or fixed points for pressure caUbration exist and are analogous to the temperature standards cited (23). These points are based on phase changes or resistance jumps in selected materials. For the highest pressures, the most rehable technique is the correlation of the wavelength shift, /SX with pressure of the mby, R, fluorescence line and is determined by simultaneous specific volume measurements on cubic metals... 

The force exerted on a submerged planar surface of area A is given by F = p A where p is the pressure at the geometrical centroid of the surface. The center of pressure, the point of application of the net force, is always lower than the centroid. For details see, for example. Shames, where may also be found discussion of forces on curved surfaces, buoyancy, and stability of floating bodies. 

Pressure The force per unit of area exerted in all directions by a gas or liquid on the walls of its container. 

An arch dam, on the other hand, relies on its shape to withstand the pressure of the water behind it. The arch curves back upstream and the force exerted by the water is transferred through the dam into the river valley walls and to the river floor. They are normally constructed in deep gorges where the geological foundations are veiy sound. The United States s Hoover Dam is an example of a concrete arch dam. 

FIGURE 4.24 In the kinetic model of gases, the pressure arises from the force exerted on the walls of the container when the impacting molecules are deflected. We need to know the force of each impact and the number of impacts in a given time interval. 

The mercury does fall, but the flow stops at a fixed height. The column of mercury stops falling because the atmosphere exerts pressure on the mercury in the dish, pushing the column up the tube. The column is in balance when the height of the mercury column generates a downward force on the inside of the tube that exactly balances the force exerted by the atmosphere on the outside of the tube. 

Molecular speed affects pressure in two ways that are illustrated in Figure 5-12. First, faster-moving molecules hit the walls more often than slower-moving molecules. The number of collisions each molecule makes with the wall is proportional to the molecule s speed. Second, the force exerted when a molecule strikes the wall depends on the molecule s speed. A fast-moving molecule exerts a larger force than the same molecule moving slower. Force per collision increases with speed, and number of collisions increase with speed, so the total effect of a single molecule on the pressure of a gas is proportional to the square of its speed. 

Whenever a chemical process occurs at constant pressure, the volume can change, particularly when gases are involved. In a constant-pressure calorimeter, for instance, the chemical system may expand or contract. In this change of volume, the system moves against the force exerted by the constant pressure. Because work is force times displacement, w = F d, this means that work is done whenever a volume change occurs at constant pressure. 

Reciprocating compressors compress gases by a piston moving backwards and forwards in a cylinder. Valves control the flow of low-pressure gas into the cylinder and high-pressure gas out of the cylinder. The mechanical work to compress a gas is the product of the external force acting on the gas and the distance through which the force moves. Consider a cylinder with cross-sectional area A containing a gas to be compressed by a piston. The force exerted on the gas is the product of the pressure (force per unit area) and the area A of the piston. The distance the piston travels is the volume V of the cylinder divided by the area A. Thus ... 

In steady state, the velocity of the gas is constant, and there is no net force on the gas. The force exerted on the gas by the wall, Fwg, is balanced by the volume force from the pressure difference. If the pressure on the high pressure end of the tube is P, and the pressure on the low pressure end is P", the volume force is CP P")na2. Setting the two balancing forces equal to each other then gives the equation... 

The force exerted on a solid boundary by a static pressure is given by... 

Note that both force and area are vectors, whereas pressure is a scalar. Hence the directional character of the force is determined by the orientation of the surface on which the pressure acts. That is, the component of force acting in a given direction on a surface is the integral of the pressure over the projected component area of the surface, where the surface vector (normal to the surface component) is parallel to the direction of the force [recall that pressure is a negative isotropic stress and the outward normal to the (fluid) system boundary represents a positive area]. Also, from Newton s third law ( action equals reaction ), the force exerted on the fluid system boundary is of opposite sign to the force exerted by the system on the solid boundary. 

Further cost reductions are possible if the pressure sensor can be fastened to the vibrating suds container instead of requiring an additional component Pressure sensors normally measure the force exerting pressure on a defined surface. Depending on the principle of the particular pressure sensor, it will require an accelerating mass which, when accelerated, produces an additional force and the resulting acceleration signal. Three possible examples are described below. 

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