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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 instantaneous velocity equation comes from finding the limit as t approaches 0 of the average velocity. The instantaneous velocity shows the position function with respect to time. From the instantaneous velocity the instantaneous speed can be derived by getting the magnitude of the instantaneous velocity.
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 ...
In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or, if one body is much more massive than the other bodies of the system combined, its speed relative to the center of mass of the most massive body.
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 ...
where is the instantaneous speed of the particle, the Lorentz factor, is the speed of light, and is the coordinate time. Solving for the equation of motion gives the desired formulas, which can be expressed in terms of coordinate time T {\displaystyle T} as well as proper time τ {\displaystyle \tau } .
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).
Speed is a scalar, being the magnitude of the velocity vector which in relativity is the four-velocity and in three-dimension Euclidean space a three-velocity. Speed is empirically measured as average speed, although current devices in common use can estimate speed over very small intervals and closely approximate instantaneous speed.