Fluid Power

Anything that has mass and takes up space

• Force per unit area
• Pounds per square in

• The measure of a body’s resistance to acceleration
• Different from but proportional to weight

The gravitational force exerted on an object

Amount of mass per unit volume

• Pressure due to the weight of the atmosphere above a certain point.
• Approximately 14.7 psi at sea level
• Lubbock is approximately 13.9 psi

• Density of a fluid referenced to:
• Air if it is a gas
• Water if it is a liquid

• Referenced to a complete vacuum
• Equals gage pressure plus atmospheric pressure for positive pressures
• 585 psig + 14.7 psia = 599.7 psia
• Equals Complete vacuum minus gage vacuum for vacuums
• 29.92 in Hg – 26 in Hg = 3.92 in Hg

• Temperature referenced to absolute zero
• -273oC = 0 Kelvin
• -459.7oF=0 Rankine

Point at which all molecular motion stops

A state of balance between two opposing actions

The change in volume of a unit volume of a fluid when it is subjected to a unit change of pressure

The action of one body on another tending to change the velocity of the body acted upon

• The action of one body or substance rubbing against another, such as fluid flowing against the walls of pipe
• The resistance to motion caused by this rubbing

The tendency of a body at rest to remain at rest, and a body in motion to continue to move at a constant speed along a straight line, unless the body is acted upon in either case by an unbalanced force

The ability or capacity to do work

• Anything that has the ability to flow
• A liquid or gas

A change in the volume of a substance due to a change in its temperature

• The rate of motion in a particular direction
• The velocity of fluids is usually expressed in feet per second

• The rate of doing work
• The rate of expanding energy
• Power = Work/Time

• The transference of energy from one body or system to another
• That which is accomplished by a force acting through a distance
• Work = Force * Distance

• The absolute pressure of a fixed mass of gas varies inversely as the volume, provided the temperature remains constant.
• P1V1=P2V2

• If the pressure is constant, the volume of dry gas will vary directly with the absolute temperature.
• V1/T1=V2/T2

• At the same temperature and pressure, equal volumes of different gases contain equal numbers of molecules.
• 6.023x1023 atoms per mole
• Mole – The amount of pure substance that contains the same number of elementary entities as there are atoms in exactly 12 grams of the isotope carbon 12

A mixture of several gases which do not react chemically exerts a pressure equal to the sum of the pressures which the several gases would exert separately if each were allowed to occupy the entire space alone at the given temperature.

A pressure applied to a confined fluid at rest is transmitted with equal intensity throughout the fluid

• Pressure is inversely proportional to velocity.
• An increase in velocity of a fluid will cause decrease in pressure

• 1ST: A body at rest tends to stay at rest and a body in motion tends to stay in motion
• 2ND: An imbalance of force on a body tends to produce an acceleration in the direction of the force. This acceleration is directly proportional to the force and inversely proportional to the mass of the body F=mA
• 3RD: For every action there is an equal and opposite reaction