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Viscosity The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress.[1] For liquids, it corresponds to the informal concept of "thickness"; for example, honey has higher viscosity than water.[2] Viscosity Viscosity is a property of the fluid which opposes the relative motion between the two surfaces of the fluid that are moving at different velocities. In simple terms, viscosity means friction between the molecules of fluid. When the fluid is forced through a tube, the particles which compose the fluid generally move more quickly near the tube's axis and more slowly near its walls; therefore some stress (such as a pressure difference between the two ends of the tube) is needed to overcome the friction between particle layers to keep the fluid moving [...More...] 


Second The second is the SI base unit SI base unit of time, commonly understood and historically defined as 1/86,400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each. Another intuitive understanding is that it is about the time between beats of a human heart.[nb 1] Mechanical and electric clocks and watches usually have a face with 60 tickmarks representing seconds and minutes, traversed by a second hand and minute hand. Digital clocks and watches often have a twodigit counter that cycles through seconds [...More...] 


Defining Equation (physics) In physics, defining equations are equations that define new quantities in terms of base quantities.[1] This article uses the current SI system of units, not natural or characteristic units.Contents1 Description of units and physical quantities1.1 Colour mixing analogy2 Motivation 3 Construction of defining equations3.1 Scope of definitions 3.2 Multiple choice definitions4 Limitations of definitions 5 Oneoff definitions 6 See also 7 Footnotes 8 Sources 9 Further readingDescription of units and physical quantities[edit] Physical quantities and units follow the same hierarchy; chosen base quantities have defined base units, from these any other quantities may be derived and have corresponding derived units. Colour mixing analogy[edit] Defining quantities is analogous to mixing colours, and could be classified a similar way, although this is not standard. Primary colours are to base quantities; as secondary (or tertiary etc.) colours are to derived quantities [...More...] 


Linear Function In mathematics, the term linear function refers to two distinct but related notions:[1]In calculus and related areas, a linear function is a polynomial function of degree zero or one, or is the zero polynomial.[2] In linear algebra and functional analysis, a linear function is a linear map.[3]Contents1 As a polynomial function 2 As a linear map 3 See also 4 Notes 5 References 6 External linksAs a polynomial function[edit] Main article: Linear function Linear function (calculus)Graphs of two linear (polynomial) functions.In calculus, analytic geometry and related areas, a linear function is a polynomial of degree one or less, including the zero polynomial (the latter not being considered to have degree zero). When the function is of only one variable, it is of the form f ( x ) = a x + b , displaystyle f(x)=ax+b, where a and b are constants, often real numbers [...More...] 


Derivative The derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. For example, the derivative of the position of a moving object with respect to time is the object's velocity: this measures how quickly the position of the object changes when time advances. The derivative of a function of a single variable at a chosen input value, when it exists, is the slope of the tangent line to the graph of the function at that point. The tangent line is the best linear approximation of the function near that input value [...More...] 


Glue Adhesives, also known as glue, cement, mucilage, or paste,[1] is any substance applied to one surface, or both surfaces, of two separate items that binds them together and resists their separation.[2] Adjectives may be used in conjunction with the word "adhesive" to describe properties based on the substance's physical or chemical form, the type of materials joined, or conditions under which it is applied.[3] The use of adhesives offers many advantages over binding techniques such as sewing, mechanical fastening, thermal bonding, etc. These include the ability to bind different materials together, to distribute stress more efficiently across the joint, the cost effectiveness of an easily mechanized process, an improvement in aesthetic design, and increased design flexibility [...More...] 


Mistletoe Mistletoe Mistletoe is the English common name for most obligate hemiparasitic plants in the order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they absorb water and nutrients from the host plant. The name mistletoe originally referred to the species Viscum album (European mistletoe, of the family Santalaceae Santalaceae in the order Santalales); it was the only species native to Great Britain Great Britain and much of Europe [...More...] 


Latin Latin Latin (Latin: lingua latīna, IPA: [ˈlɪŋɡʷa laˈtiːna]) is a classical language belonging to the Italic branch of the IndoEuropean languages. The Latin alphabet Latin alphabet is derived from the Etruscan and Greek alphabets, and ultimately from the Phoenician alphabet. Latin Latin was originally spoken in Latium, in the Italian Peninsula.[3] Through the power of the Roman Republic, it became the dominant language, initially in Italy and subsequently throughout the Roman Empire. Vulgar Latin Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Greek and French have contributed many words to the English language [...More...] 


Perpendicular In elementary geometry, the property of being perpendicular (perpendicularity) is the relationship between two lines which meet at a right angle (90 degrees). The property extends to other related geometric objects. A line is said to be perpendicular to another line if the two lines intersect at a right angle.[2] Explicitly, a first line is perpendicular to a second line if (1) the two lines meet; and (2) at the point of intersection the straight angle on one side of the first line is cut by the second line into two congruent angles. Perpendicularity can be shown to be symmetric, meaning if a first line is perpendicular to a second line, then the second line is also perpendicular to the first. For this reason, we may speak of two lines as being perpendicular (to each other) without specifying an order. Perpendicularity easily extends to segments and rays [...More...] 


Isaac Newton Sir Isaac Newton Isaac Newton PRS (/ˈnjuːtən/;[6] 25 December 1642 – 20 March 1726/27[1]) was an English mathematician, astronomer, theologian, author and physicist (described in his own day as a "natural philosopher") who is widely recognised as one of the most influential scientists of all time, and a key figure in the scientific revolution. His book Philosophiæ Naturalis Principia Mathematica ("Mathematical Principles of Natural Philosophy"), first published in 1687, laid the foundations of classical mechanics. Newton also made pathbreaking contributions to optics, and he shares credit with Gottfried Wilhelm Leibniz Gottfried Wilhelm Leibniz for developing the infinitesimal calculus. Newton's Principia formulated the laws of motion and universal gravitation that dominated scientists' view of the physical universe for the next three centuries [...More...] 


Differential Equation A differential equation is a mathematical equation that relates some function with its derivatives. In applications, the functions usually represent physical quantities, the derivatives represent their rates of change, and the differential equation defines a relationship between the two. Because such relations are extremely common, differential equations play a prominent role in many disciplines including engineering, physics, economics, and biology. In pure mathematics, differential equations are studied from several different perspectives, mostly concerned with their solutions—the set of functions that satisfy the equation. Only the simplest differential equations are solvable by explicit formulas; however, some properties of solutions of a given differential equation may be determined without finding their exact form. If a closedform expression for the solution is not available, the solution may be numerically approximated using computers [...More...] 


Cryogenics In physics, cryogenics is the production and behaviour of materials at very low temperatures. It is not welldefined at what point on the temperature scale refrigeration ends and cryogenics begins, but scientists[1] assume a gas to be cryogenic if it can be liquefied at or below −150 °C (123.15 K; −238.00 °F). The U.S. National Institute of Standards and Technology has chosen to consider the field of cryogenics as that involving temperatures below −180 °C (93.15 K; −292.00 °F) [...More...] 


IUPAC The International International Union of Pure and Applied Chemistry Chemistry (IUPAC) /ˈaɪjuːpæk/ or /ˈjuːpæk/ is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International International Council for Science (ICSU).[2] IUPAC is registered in Zürich, Switzerland, and the administrative office, known as the "IUPAC Secretariat", is in Research Triangle Park, North Carolina, United States. This administrative office is headed by IUPAC's executive director,[3] currently Lynn Soby.[4] IUPAC was established in 1919 as the successor of the International Congress of Applied Chemistry Chemistry for the advancement of chemistry. Its members, the National Adhering Organizations, can be national chemistry societies, national academies of sciences, or other bodies representing chemists [...More...] 


Pascal (unit) The pascal (symbol: Pa) is the SI derived unit SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus Young's modulus and ultimate tensile strength [...More...] 


Density The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:[1] ρ = m V displaystyle rho = frac m V where ρ is the density, m is the mass, and V is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume,[2] although this is scientifically inaccurate – this quantity is more specifically called specific weight. For a pure substance the density has the same numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity and packaging [...More...] 


Velocity The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is equivalent to a specification of its speed and direction of motion (e.g. 7001600000000000000♠60 km/h to the north). Velocity Velocity is an important concept in kinematics, the branch of classical mechanics that describes the motion of bodies. Velocity Velocity is a physical vector quantity; both magnitude and direction are needed to define it. The scalar absolute value (magnitude) of velocity is called "speed", being a coherent derived unit whose quantity is measured in the SI (metric system) as metres per second (m/s) or as the SI base unit of (m⋅s−1). For example, "5 metres per second" is a scalar, whereas "5 metres per second east" is a vector [...More...] 
