Fad

A fad or trend is any form of behavior that develops among a large population and is collectively followed enthusiastically for a period of time, generally as a result of the behavior being perceived as popular by one's peers or being deemed "cool" by social or other media. A fad is said to "catch on" when the number of people adopting it begins to increase rapidly. They normally fade quickly once the perception of novelty is gone.

Overview

The specific nature of the behavior associated with a fad can be of any type including language usage, apparel, financial investment and even food. Apart from general novelty, fads may be driven by mass media programming, emotional excitement, peer pressure, or the desire to "be hip". Fads may also be set by popular celebrities.

Though the term trend may be used interchangeably with fad, a fad is generally considered a quick and short behavior whereas a trend is considered to be a behavior that evolves into a relatively permanent change.

In economics, the term is used in a similar way. Fads are mean-reverting deviations from intrinsic value caused by social or psychological forces like those that cause fashions in political beliefs or consumption goods.

Alan Walker

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See also

Flavin adenine dinucleotide

In biochemistry, flavin adenine dinucleotide (FAD) is a redox cofactor, more specifically a prosthetic group, involved in several important reactions in metabolism. FAD can exist in three (or four: flavin-N(5)-oxide) different redox states, which are the quinone, semiquinone, and hydroquinone. FAD is converted between these states by accepting or donating electrons.

FAD, in its fully oxidized form, or quinone form, accepts two electrons and two protons to become FADH₂ (hydroquinone form). The semiquinone (FADH^·) can be formed by either reduction of FAD or oxidation of FADH₂ by accepting or donating one electron and one proton, respectively. See the mechanism section below for details.

A flavoprotein is a protein that contains a flavin moiety, this may be in the form of FAD or flavin mononucleotide (FMN). There are many flavoproteins besides components of the succinate dehydrogenase complex, including α-ketoglutarate dehydrogenase and a component of the pyruvate dehydrogenase complex, some examples are shown in section 6.

Bullet

A bullet is a projectile propelled by a firearm, sling, slingshot, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration. The word "bullet" is sometimes colloquially used to refer to ammunition in general, or to a cartridge, which is a combination of the bullet, case/shell, powder, and primer. This use of 'bullet', when 'cartridge' is intended, leads to confusion when the components of a cartridge are discussed or intended.

Bullets fired from slings, slingshots, and many airguns (including BB guns) travel well below the speed of sound (about 343 m/s or 1126 ft/s in dry air at 20 °C or 68 °F). Low-power handguns have muzzle velocities generally less than the speed of sound (subsonic), while bullets fired from high-power handguns (such as a .44 Magnum) and from rifles have an initial speed faster than the speed of sound, meaning they are supersonic and thus can travel a substantial distance and even hit a target before a nearby observer hears the "bang" of the shot. Bullet speed through air depends on a number of factors such as barometric pressure, humidity, air temperature, and wind speed.

Force

In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described by intuitive concepts such as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F.

The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object

Related concepts to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object. In an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the so-called mechanical stress. Pressure is a simple type of stress. Stress usually causes deformation of solid materials, or flow in fluids.