![]() ![]() Molecules in fluids come in different sizes: solvent molecules approx. ![]() Why do different substances have different viscosities? Larger components present in a fluid are the reason for higher viscosity values. They develop a flow resistance caused by internal friction. When put into motion, molecules and particles are forced to slide along each other. Rheometry is the measuring technology used to determine rheological properties.Īll liquids are composed of molecules dispersions also contain some significantly larger particles. The term “rhei” indicates that the content of the bottle is liquid.). Exhibited in the German Apotheken-Museum, Heidelberg. The term originates from the Greek word “rhei” meaning “to flow” (Figure 1.1: Bottle from the 19th century bearing the inscription “Tinct(ur) Rhei Vin(um) Darel”. Rheologists describe the deformation and flow behavior of all kinds of material. The radian is the SI unit for measuring angles, and is the standard unit of angular measure used in many areas of mathematics.Ī degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle, defined so that a full rotation is 360 degrees.Rheology is a branch of physics. One tesla is equal to one weber per square metre The tesla (symbol T) is a derived unit of the magnetic field strength (also, magnetic flux density) in the International System of Units. The SI unit of acceleration is the metre per second squared (m s−2), or metre per second per second, as the velocity in metres per second changes by the acceleration value, every second. The volt (symbol: V) is the derived unit for electric potential, electric potential difference, and electromotive force. The decibel is a unit of measurement used to express the ratio of one value of a physical property to another on a logarithmic scale. The torr (symbol: Torr) is a unit of pressure based on an absolute scale, now defined as exactly 1/760 of a standard atmosphere (101325 Pa). It is named after the French polymath Blaise Pascal. It is defined as one newton per square metre. The pascal is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength. It is defined as exactly equal to 100,000 Pa, which is slightly less than the current average atmospheric pressure on Earth at sea level The bar is a metric unit of pressure, but is not approved as part of the International System of Units (SI). It is sometimes used as a reference or standard pressure The standard atmosphere is a unit of pressure defined as 101325 Pa (1.01325 bar). ![]() The knot is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.15078 mph) It is by international agreement in 1959 standardized as exactly 0.9144 meters. The yard is an English unit of length, in both the British imperial and US customary systems of measurement, that comprises 3 feet or 36 inches. In both systems, the foot comprises 12 inches and three feet compose a yard. Since 1959, both units have been defined by international agreement as equivalent to 0.3048 meters exactly. The foot is a unit of length in the imperial and US customary systems of measurement. It is equal to 1⁄36 yard or 1⁄12 of a foot. The inch is a unit of length in the (British) imperial and United States customary systems of measurement. The mile is an English unit of length of linear measure equal to 5,280 feet, or 1,760 yards, and standardised as exactly 1,609.344 metres by international agreement in 1959. The meter is the base unit of length in some metric systems, including the International System of Units (SI). The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero,the temperature at which all thermal motion ceases in the classical description of thermodynamics.The kelvin (symbol: K) is the base unit of temperature in the International System of Units (SI). The Fahrenheit scale is a temperature scale based on one proposed in 1724 by Dutch–German–Polish physicist Daniel Gabriel Fahrenheit (1686–1736). Temperatures on the centigrade scale were often reported simply as degrees or, when greater specificity was desired, as degrees centigrade (symbol: ☌). Since the 19th century, the scientific and thermometry communities worldwide have used the phrase centigrade scale. ![]()
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