Topic 2B Flashcards
Density equation
Density = mass/volume
Specific gravity equation
specific gravity = density of material / density of water
buoyancy
it’s the ratio of the density of a substance to the density of a reference substance; equivalently, it’s the ratio of the mass of a substance to the mass of a
reference substance for the same given volume”
Archimedes principle
the buoyant force exerted on a body immersed in a fluid is equal to the weight of the fluid the body displaces
Fobject = Wfluid
Pressure formula
Pressure = force/ unit area
Hydrostatic pressure formula
Fluid pressure = (fluid density)(acceleration d/t gravity)(fluid depth)
Pascal’s Principle/Pascal’s Law
applies to static fluids and takes advantage of the height dependency of pressure in static fluids. Pascal’s Principle can be used to exploit pressure of a static liquid as a measure of energy per unit volume to perform work in applications such as hydraulic presses.
Viscosity formula
Viscosity = [(Force)(distance b/t the plates)] / [(constant velocity)(Area of the plate)]
Poiseuille flow
pressure-induced flow in a long duct, usually a pipe. It is assumed that there is a laminar flow of an incompressible fluid of viscosity η
Flow rate Q- Poiseuille’s
Volumetric flow rate- Q,v, A and Q, V, t
Q=velocity of fluid x area of the cross-section of the space the fluid is moving through
Q = Volume/ elapsed time
Reynolds number (NR)
the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities; dimensionless quantity It can reveal whether flow is laminar or turbulent. For flow in a tube of uniform diameter, the Reynolds number is defined as:
NR = [(2fluid densityspeed*tube radius)] / [(viscosity)]
Reynolds number around what is laminar and around what is turbulent
around 2000 is laminar and around 3000 is turbulent and between 2000-3000 is unstable
Surface tension
s proportional to the strength of the cohesive force, which varies with the type of liquid. It’s the reason why liquids form bubbles and droplets. The inward surface tension force causes bubbles to be approximately spherical and raises the pressure of the gas trapped inside relative to atmospheric pressure outside.
γ = force / unit length L exerted by a stretched liquid membrane:
Cohesive forces
(IMF’s within a fluid) are stronger, then surface of fluid is convex
Adhesive forces
(IMF’s between a fluid and the tube) are stronger, the surface of fluid is concave
Bernoulli’s equation:
The relationship between pressure and velocity in fluids
Situation where the fluid is static—that is, v 1 = v 2 = 0. In that case, we get
P2=P1 + density(g)(height1)
Situation where the fluid moves but its depth is constant—that is, h 1 = h2 . Bernoulli’s equation becomes:
Pitot tube
a horizontal tube that contains a U-shaped tube.
◦ The surface of the pitot tube has at least two openings, one of which faces directly into the fluid flow. The first opening encounters fluid with a velocity of zero. The pressure at this opening is equal to the static pressure exerted by the fluid.
Venturi tube
A Venturi tube is a horizontal tube with a constricted region (decreased cross-sectional area) in its middle. It can be used to determine the velocity of a fluid that is flowing within it. This is in contrast to a pitot tube, which is used to determine the velocity of a fluid flowing past it.
Ideal Gas Equation
(Pressure)(Volume) = (#moles)(Ideal gas constant)(Temperature)
what are the 3 most common forms of R used as the ideal gas constant
8.3145 LkPa/Kmol; 0.0821 Latm/Kmol; 62.4 LmmHg/Kmol
Boyle’s law
P1V1 = P2V2
Charles’ law
V1/T1 = V2/T2
Avogadro’s law
Volume * #moles = proportionality constant
Kinetic Molecular Theory of Gases:
◦ The volume occupied by the individual particles of a gas is negligible compared to the volume of the gas itself.
◦ The particles of an ideal gas exert no attractive forces on each other or on their surroundings.
◦ Gas particles are in a constant state of random motion and move in straight lines until they collide with another body.
◦ The collisions exhibited by gas particles are completely elastic; when two molecules collide, total kinetic energy is conserved.
◦ The average kinetic energy of gas molecules is directly proportional to absolute temperature only; this implies that all molecular motion ceases if the temperature is reduced to absolute zero.
Heat capacity/adiabatic index /thermal capacity
the measurable physical quantity that characterizes the amount of heat required to change a substance’s T by a given amount. An object’s heat capacity (C) is defined as the ratio of the amount of heat energy transferred to an object to the resulting ↑ in T of the object.
heat energy equation
heat energy = mass * specific heat capacity * change in temperature
