Laws Of Physics Flashcards
BOYLES LAW
The principle that the volume of a given mass of an ideal gas is inversely proportional to its pressure, as long as temperature remains constant.
CHARLES LAW
The principle that the volume of a given mass of an ideal gas is proportional to its temperature as long as its pressure remains constant.
ARCHIMEDES’ (buoyancy)
Liquids exert buoyant force because the pressure below a submerged object always exceeds the pressure above it. The bouyant force must equal the weight of the fluid displaced by the object. If the weight density of an object is less than that of water (1g/cm3), it will displace a weight of water greater than its own weight. In this case, the upward buoyant force will overcome gravity, and the object will float. Conversely, if an objects weight density exceeds the weight of water, the object will sink. (Because the weight of fluid displaced by an object equals its weight density x it’s volume (Dw=V), the buoyant force (B) may be calculated B = Dw x V
Laplace’s Law
a principle of physics that the tension on the wall of a sphere is the product of the pressure times the radius of the chamber and the tension is inversely related to the thickness of the wall.
Surface tension like a fist compressing a ball, increases the pressure inside a liquid drop or bubble. This pressure varies directly with the surface tension of the liquid and inversely with its radius. 4ST
P= —–
R
AVOGADRO’S LAW
A law in physics stating that equal volumes of all gases at a given temperature and pressure contain the identical number of particles.
1-g atomic weight of any substance contains exactly the same # of atoms, molecules or ions. 6.023 x 10 to 23 power is avogadro’s constant. In SI units this quantity = 1 mole
GRAHAM’S LAW
The law stating that the rate of diffusion of a gas through a liquid (or the alveolar-capillary membrane) is directly proportional to its solubility coefficient and inversely proportional to the square root of its density.
Gas diffusion rates are quantified using this law. Mathematically, the rate of diffusion of a gas (D) is inversely proportional to the square root of its gram molecular weight.
1
Dgas = ——
Divided by gmw
According to this principle, lighter gases diffuse rapidly, whereas heavy gases diffuse more slowly. Diffusion is based on kinetic activity, anything that increases molecular activity, will quicken diffusion.
HENRY’S LAW
The solubility of a gas in a liquid solution at a constant temperature is proportional to the partial pressure of the gas above the solution.
DALTON’S LAW
The pressure exerted by a mixture of nonreacting gases is equal to the sum of the partial pressures of the separate components; it holds true only at very low pressures.
GAY LUSSACS LAW
Simply put, if a gas’ temperature increases, then so does its pressure if the mass and volume of the gas are held constant. The law has a particularly simple mathematical form if the temperature is measured on an absolute scale, such as in kelvins. The law can then be expressed mathematically as:
P
– = k
T
where:
P is the pressure of the gas
T is the temperature of the gas (measured in Kelvin).
k is a constant.
This law holds true because temperature is a measure of the average kinetic energy of a substance; as the kinetic energy of a gas increases, its particles collide with the container walls more rapidly, thereby exerting increased pressure.
For comparing the same substance under two different sets of conditions, the law can be written as:
P1 P2
— = —
T1 T2
Because Amontons discovered the law beforehand, Gay-Lussac’s name is now generally associated within chemistry with the law of combining volumes discussed in the section above. Some introductory physics textbooks still define the pressure-temperature relationship as Gay-Lussac’s law.[7] [8] Gay-Lussac primarily investigated the relationship between volume and temperature and published it in 1802, but his work did cover some comparsion between pressure and temperature.[9] Given the relative technology to both men, Amonton was only able to work with air as a gas, where Gay-Lussac was able to experiment with multiple types of common gases, such as oxygen, nitrogen, and hydrogen.[10] Gay-Lussac did attribute his findings to Jacques Charles because he used much of Charles’s unpublished data from 1787 - hence, the law became known as Charles’s law or the Law of Charles and Gay-Lussac[11] However, in recent years the term has fallen out of favor.
POISEUILLES LAW
In fluid dynamics, the Hagen–Poiseuille equation, also known as the Hagen–Poiseuille law, Poiseuille law or Poiseuille equation, is a physical law that gives the pressure drop in a fluid flowing through a long cylindrical pipe. It can be successfully applied to air flow in lung alveoli, for the flow through a drinking straw or through a hypodermic needle. It was experimentally derived independently by Gotthilf Heinrich Ludwig Hagen in 1839 and Jean Léonard Marie Poiseuille in 1838, and published by Poiseuille in 1840 and 1846.
The assumptions of the equation are that the fluid is incompressible and newtonian; the flow is laminar through a pipe of constant circular cross-section that is substantially longer than its diameter; and there is no acceleration of fluid in the pipe. For velocities and pipe diameters above a threshold, actual fluid flow is not laminar but turbulent, leading to larger pressure drops than calculated by the Hagen–Poiseuille equation.
The difference in pressure required to produce a given flow, under conditions of laminar flow through a smooth tube of fixed size.
8n1V
P=------
r4
P is the driving pressure gradient
n is the viscosity of the fluid
1 is the tube length
V is the fluid flow
r is the tube radius
and 8 are constants
According to this formula, for fluids flowing in a laminar pattern, the driving pressure will increase whenever the fluid viscosity, tube length, or flow increases. Greater pressure will be required to maintain a given flow if the tube radius increases.
BERNOULLI PRINCIPLE / EFFECT
Bernoulli’s principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy.
Bernoulli’s principle can be applied to various types of fluid flow, resulting in what is loosely denoted as Bernoulli’s equation. In fact, there are different forms of the Bernoulli equation for different types of flow. The simple form of Bernoulli’s principle is valid for incompressible flows (e.g. most liquid flows) and also for compressible flows (e.g. gases) moving at low Mach numbers (usually less than 0.3). More advanced forms may in some cases be applied to compressible flows at higher Mach numbers (see the derivations of the Bernoulli equation).
Bernoulli’s principle can be derived from the principle of conservation of energy. This states that, in a steady flow, the sum of all forms of mechanical energy in a fluid along a streamline is the same at all points on that streamline. This requires that the sum of kinetic energy and potential energy remain constant. Thus an increase in the speed of the fluid occurs proportionately with an increase in both its dynamic pressure and kinetic energy, and a decrease in its static pressure and potential energy. If the fluid is flowing out of a reservoir, the sum of all forms of energy is the same on all streamlines because in a reservoir the energy per unit volume (the sum of pressure and gravitational potential ρ g h) is the same everywhere.[4]
Bernoulli’s principle can also be derived directly from Newton’s 2nd law. If a small volume of fluid is flowing horizontally from a region of high pressure to a region of low pressure, then there is more pressure behind than in front. This gives a net force on the volume, accelerating it along the streamline.[5][6][7]
Fluid particles are subject only to pressure and their own weight. If a fluid is flowing horizontally and along a section of a streamline, where the speed increases it can only be because the fluid on that section has moved from a region of higher pressure to a region of lower pressure; and if its speed decreases, it can only be because it has moved from a region of lower pressure to a region of higher pressure. Consequently, within a fluid flowing horizontally, the highest speed occurs where the pressure is lowest, and the lowest speed occurs where the pressure is highest.
