Friction can be defined as the force between surfaces in contact that resists their relative tangential motion (slipping). One of the simpler characteristics of friction is that it is parallel to the contact surface between systems and always in a directionthat opposes motion or attempted motion of the systems relative to each other. If two systems…

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Plasticity is the capacity to resist plastic deformation (dislocation movement of a solid material undergoing non-reversible changes of shape in response to applied forces), while toughness measures the ability of a material to resist crack propagation. The rocks, subjected to external forces, are deformed continuously and permanently, without however being subjected to rupture phenomena and…

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In geology, a rheid is a substance whose temperature is below the melting point and whose deformation by viscous flow during the time of observation is at least three orders of magnitude \((10^3)\) greater than the elastic deformation under the given conditions. A material is a rheid by virtue of the time of observation. The…

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The force may be thought of as an influence which tends to change the motion of an object. Forces are inherently vector quantities, requiring vector addition to combine them. The SI unit for force is the newton [N], which is defined by Newton = \(\dfrac{kg\cdot m}{s^2}\) as may be seen from Newton’s second law. In mechanics, forces are…

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Viscoelasticity is the study of materials which have a time-dependent strain that exhibit both viscous and elastic characteristics when undergoing deformation. Viscoelastic response is often used as a probe in polymer science, since it is sensitive to the material’s chemistry and microstructure. The identification of the viscoelastic behavior is carried out by measuring the variation…

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Anelasticity is a characteristic of viscoelastic materials that depends on some physical properties of the material itself. Anelasticity is the opposite of elasticity. An anelastic material subjected to stress undergoes deformations that are not proportional to the stresses and that do not disappear when the force is zeroed. In other words, an anelastic material will…

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Elasticity is the ability of a body to resist a distorting influence and to return to its original size and shape when that influence or force is removed. Solid objects will deform when adequate forces are applied to them. If the material is elastic, the object will return to its initial shape and size when…

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A wave is a perturbation that propagates in space and which can transport energy from one point to another. This perturbation consists of the variation of any physical quantity (for example pressure variation, temperature, electric field strength, position, etc.). Many natural phenomena are described in terms of waves. The waves in the water are together the prototype…

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Buoyancy or upthrust is an upward force exerted by a fluid that opposes the weight of an immersed object; it is what makes an object float, sink, or remain neutrally buoyant in the water (or other fluids). The symbol for the magnitude of buoyancy is \(B\) or \(F_B\). As a vector, it must be stated…

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Luminous intensity (candela) The units of luminous intensity based on flame or incandescent filament standards in use in various countries before 1948 were replaced initially by the “new candle” based on the luminance of a Planck radiator (a black body) at the temperature of freezing platinum. This modification had been prepared by the International Commission…

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Time is an abstract entity (as well as a physical quantity), useful for quantifying and measuring the passing of events. The most fundamental physical quantities are defined by how they are measured. This is the case with time. Every measurement of time involves measuring a change in some physical quantity. It may be a number…

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Weight is the force of gravity acting on an object. The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton [N]. In many real-world situations, the act of weighing may produce a result that differs from the ideal value provided by the definition used.…

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The mass (or inertial mass) represents the amount of matter that constitutes a material body, attributing dynamic characteristics (inertia) when the bodies are subject to the influence of external forces. The mass does not correspond with the amount of substance, the physical quantity for which it has been introduced in the SI a fundamental quantity, the mole…

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Energy is defined as a measurement of the ability to do work or to heat an object. Energy plays an essential role both in everyday events and in scientific phenomena (is one of the most quantitative property of physics in nature). The term energy was introduced by Aristotle in philosophy to distinguish the “power” (δύναμις,…

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To accelerate means to speed up. The greater the acceleration, the greater the change in velocity over a given time. The average acceleration is the rate at which velocity changes: \[\overline{a}=\dfrac{\Delta v}{\Delta t}=\dfrac{v_f-v_0}{t_f-t_0}\] where the bar over the acceleration \(a\) means average, \(v\) is velocity, and \(t\) is time. Acceleration is a vector in the…

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Temperature is a physical property of a material that gives a measure of the average kinetic energy of the molecular movement in an object or a system. Temperature can be defined as a condition of a body by virtue of which heat is transferred from one system to another. It is pertinent to mention here…

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Viscosity 1

The viscosity (μ) is that property of matter, defined as that physical quantity, which is found mainly in the phenomena of transport of a fluid, that describes a fluid’s resistance to flow, or more specifically, is the measure of the resistance of a fluid to gradual deformation by shear stress (τ) or tensile stress. Fluids…

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In physics, a fluid is a substance that continually deforms (flows and cannot resist deformation) under applied shear stress or external force. Fluids include gases, liquids, and plasma. All fluids are compressible (that is, their density increases under increasing pressure) to some extent, but liquids are much less compressible than gases and are generally considered…

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