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In physics and the philosophy of science, instant refers to an infinitesimal interval in time, whose passage is instantaneous.In ordinary speech, an instant has been defined as "a point or very short space of time," a notion deriving from its etymological source, the Latin verb instare, from in-+ stare ('to stand'), meaning 'to stand upon or near.' [1]
The direction of speed of point A is indicated by vector V A. Its instant center of rotation must be perpendicular to this vector (as V A is tangentially located on the circumference of a circle). The only line that fills the requirement is a line colinear with link P 1 -A. Somewhere on this line there is a point P, the instant center of ...
The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; [2] the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero. Speed is the magnitude of velocity (a vector), which indicates additionally the direction of ...
chemical physics A branch of chemistry and physics that studies chemical processes from the point of view of physics by investigating physicochemical phenomena using techniques from atomic and molecular physics and condensed matter physics. chromatic aberration circular motion classical mechanics. Also called Newtonian mechanics.
The speed at which light propagates through transparent materials, such as glass or air, is less than c; similarly, the speed of electromagnetic waves in wire cables is slower than c. The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material (n = c / v ).
What can however be experimentally measured is the round-trip speed (or "two-way" speed of light) from the source to a mirror (or other method of reflection) and back again to detector. Albert Einstein chose a synchronization convention (see Einstein synchronization ) that made the one-way speed equal to the two-way speed.
In considering motions of objects over time, the instantaneous velocity of the object is the rate of change of the displacement as a function of time. The instantaneous speed, then, is distinct from velocity, or the time rate of change of the distance travelled along a specific path. The velocity may be equivalently defined as the time rate of ...
The TKE can be defined to be half the sum of the variances σ² (square of standard deviations σ) of the fluctuating velocity components: = (+ +) = ((′) ¯ + (′) ¯ + (′) ¯), where each turbulent velocity component is the difference between the instantaneous and the average velocity: ′ = ¯ (Reynolds decomposition).