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Skid Marks
A skid mark is the visible mark left by any solid which moves against another, and is an important aspect of trace evidence analysis in forensic science and forensic engineering. Skid marks caused by tires on roads occur when a vehicle wheel stops rolling and slides or spins on the surface of the road. Skid marks can be analyzed to find the maximum and minimum vehicle speed prior to an impact or incident. Skid (automobile), Skidding can also occur on black ice or Diesel fuel, diesel deposits on the road and may not leave a mark at all. Characteristics Skid marks are divided into "acceleration marks" created on acceleration, if the engine provides more power than the tire can transmit; "braking marks", if the brakes "lock up" and cause the tire to slide; or "yaw (rotation), yaw marks", if the tire slides sideways. Each skid mark has a characteristic appearance, and an experienced accident reconstructor or forensic engineer can often determine what the vehicle was doing by exami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has a great affinity towards oxygen, passivation (chemistry), forming a protective layer of aluminium oxide, oxide on the surface when exposed to air. It visually resembles silver, both in its color and in its great ability to reflect light. It is soft, magnetism, nonmagnetic, and ductility, ductile. It has one stable isotope, 27Al, which is highly abundant, making aluminium the abundance of the chemical elements, 12th-most abundant element in the universe. The radioactive decay, radioactivity of aluminium-26, 26Al leads to it being used in radiometric dating. Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foot (unit)
The foot (standard symbol: ft) is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, , is commonly used to represent the foot. In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet. Since an international agreement in 1959, the foot is defined as equal to exactly 0.3048 meters. Historically, the "foot" was a part of many local systems of units, including the Greek, Roman, Chinese, French, and English systems. It varied in length from country to country, from city to city, and sometimes from trade to trade. Its length was usually between 250 mm and 335 mm and was generally, but not always, subdivided into 12 inches or 16 digits. The United States is the only industrialized country that uses the (international) foot in preference to the meter in its commercial, engineering, and standards activities. The foot is legally recognized in the Uni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Miles Per Hour
Miles per hour (mph, m.p.h., MPH, or mi/h) is a British imperial and United States customary unit of speed expressing the number of miles travelled in one hour. It is used in the United Kingdom, the United States, and a number of smaller countries, most of which are UK or US territories, or have close historical ties with the UK or US. Usage Road traffic Speed limits and road traffic speeds are given in miles per hour in the following jurisdictions: *Antigua and Barbuda *Bahamas *Belize *Dominica *Grenada *Liberia (occasionally) *Marshall Islands *Micronesia *Palau *Saint Kitts and Nevis *Saint Lucia *Saint Vincent and the Grenadines *United Kingdom *The following British Overseas Territories: **Anguilla **British Virgin Islands **British Indian Ocean Territory **Cayman Islands **Falkland Islands **Montserrat **Saint Helena, Ascension and Tristan da Cunha **Turks and Caicos Islands *The Crown dependencies: **Bailiwick of Guernsey **Isle of Man **Jersey *United States ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Customary Units
United States customary units form a system of measurement units commonly used in the United States and most U.S. territories since being standardized and adopted in 1832. The United States customary system developed from English units that were in use in the British Empire before the U.S. became an independent country. The United Kingdom's system of measures evolved by 1824 to create the imperial system (with imperial units), which was officially adopted in 1826, changing the definitions of some of its units. Consequently, while many U.S. units are essentially similar to their imperial counterparts, there are noticeable differences between the systems. The majority of U.S. customary units were redefined in terms of the meter and kilogram with the Mendenhall Order of 1893 and, in practice, for many years before. T.C. Mendenhall, Superintendent of Standard Weights and MeasuresOrder of April 5, 1893, published as Appendix 6 to the Report for 1893 of the United States Coast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metre
The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of of a second, where the second is defined by a hyperfine transition frequency of caesium. The metre was originally defined in 1791 by the French National Assembly as one ten-millionth of the distance from the equator to the North Pole along a great circle, so the Earth's polar circumference is approximately . In 1799, the metre was redefined in terms of a prototype metre bar. The bar used was changed in 1889, and in 1960 the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton-86. The current definition was adopted in 1983 and modified slightly in 2002 to clarify that the metre is a measure of proper length. From 1983 until 2019, the metre was formally defined as the length of the path trave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Km/h
The kilometre per hour ( SI symbol: km/h; non-SI abbreviations: kph, kmph, km/hr) is a unit of speed, expressing the number of kilometres travelled in one hour. History Although the metre was formally defined in 1799, the term "kilometres per hour" did not come into immediate use – the myriametre () and myriametre per hour were preferred to kilometres and kilometres per hour. In 1802 the term "''myriamètres par heure''" appeared in French literature. The Dutch on the other hand adopted the kilometre in 1817 but gave it the local name of the ''mijl'' ( Dutch mile). Notation history The SI representations, classified as symbols, are "km/h", "" and "". Several other abbreviations of "kilometres per hour" have been used since the term was introduced and many are still in use today; for example, dictionaries list "kph","kph." '' |
International System Of Units
The International System of Units, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official status in nearly every country in the world, employed in science, technology, industry, and everyday commerce. The SI system is coordinated by the International Bureau of Weights and Measures, which is abbreviated BIPM from . The SI comprises a coherent system of units of measurement starting with seven base units, which are the second (symbol s, the unit of time), metre (m, length), kilogram (kg, mass), ampere (A, electric current), kelvin (K, thermodynamic temperature), mole (mol, amount of substance), and candela (cd, luminous intensity). The system can accommodate coherent units for an unlimited number of additional quantities. These are called coherent derived units, which can always be represented as products of powers of the base u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metric System
The metric system is a system of measurement that standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules governing the metric system have changed over time, the modern definition, the International System of Units (SI), defines the metric prefixes and seven base units: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd). An SI derived unit is a named combination of base units such as hertz (cycles per second), newton (kg⋅m/s2), and tesla (1 kg⋅s−2⋅A−1) and in the case of Celsius a shifted scale from Kelvin. Certain units have been officially accepted for use with the SI. Some of these are decimalised, like the litre and electronvolt, and are considered "metric". Others, like the astronomical unit are not. Ancient non-metric but SI-accepted multiples of time, minute and hour, are base 60 (sexagesimal). Simil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inverse Function
In mathematics, the inverse function of a function (also called the inverse of ) is a function that undoes the operation of . The inverse of exists if and only if is bijective, and if it exists, is denoted by f^ . For a function f\colon X\to Y, its inverse f^\colon Y\to X admits an explicit description: it sends each element y\in Y to the unique element x\in X such that . As an example, consider the real-valued function of a real variable given by . One can think of as the function which multiplies its input by 5 then subtracts 7 from the result. To undo this, one adds 7 to the input, then divides the result by 5. Therefore, the inverse of is the function f^\colon \R\to\R defined by f^(y) = \frac . Definitions Let be a function whose domain is the set , and whose codomain is the set . Then is ''invertible'' if there exists a function from to such that g(f(x))=x for all x\in X and f(g(y))=y for all y\in Y. If is invertible, then there is exactly one functi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Braking Distance
A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Background Most brakes commonly use friction between two surfaces pressed together to convert the kinetic energy of the moving object into heat, though other methods of energy conversion may be employed. For example, regenerative braking converts much of the energy to electrical energy, which may be stored for later use. Other methods convert kinetic energy into potential energy in such stored forms as pressurized air or pressurized oil. Eddy current brakes use magnetic fields to convert kinetic energy into electric current in the brake disc, fin, or rail, which is converted into heat. Still other braking methods even transform kinetic energy into different forms, for example by transferring the energy to a rotating flywheel. Brakes are generally a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Judicial Notice
Judicial notice is a rule in the law of evidence that allows a fact to be introduced into evidence if the truth of that fact is so notorious or well-known, or so authoritatively attested, that it cannot reasonably be doubted. This is done upon the request of the party seeking to rely on the fact at issue. Facts and materials admitted under judicial notice are accepted without being formally introduced by a witness or other rule of evidence, even if one party wishes to plead evidence to the contrary. Judicial notice is frequently used for the simplest, most obvious common sense facts, such as which day of the week corresponded to a particular calendar date or the approximate time at sunset. However, it could even be used within one jurisdiction to notice a law of another jurisdiction—such as one which provides average baselines for motor vehicle stopping distances. Judicial notice in the United States Judicial notice in the Federal Rules of Evidence In the United States, Article ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
