Instantaneous speed: concept, calculation formula, recommendations for finding

Speed in physics means the speed of moving an object (a material point) in space. This value can be different: linear, angular, average, cosmic and even superluminal. Among all the existing varieties is also the instantaneous speed. What is this value, what is its formula and what actions are necessary for its calculation - this is exactly what will be discussed in our article.

Instantaneous speed: essence and concept

How to determine the speed of the movement of an object along a straight line is known even to the pupil of the initial classes: it is enough to cover the distance traveled by the time that was spent for such a move. However, it is worth remembering that the result obtained in this way allows you to judge the average value. If the object moves unevenly, then in certain parts of its path the speed of movement can vary considerably. Therefore, sometimes such a quantity as instantaneous speed is required. It allows you to judge the speed of the movement of a material point at any moment of motion.

Instantaneous speed: calculation formula

This parameter is equal to the limit (denoted limit, abbreviated lim) of the displacement ratio (coordinate difference) to the time interval for which this change occurred, provided that this time interval tends to reach zero. This definition can be written in the form of the following formula:

V = Δs / Δt for Δt → 0 or so v = lim _{Δt → 0} (Δs / Δt)

Note that the instantaneous velocity is a vector quantity. If the motion occurs in a straight line, then it changes only in magnitude, and the direction remains constant. Otherwise, the velocity vector of the instantaneous is directed along the tangent with respect to the trajectory of displacement at each considered point. What is the meaning of this indicator? Instantaneous speed makes it possible to find out what kind of movement the object will perform per unit of time, if from the moment under consideration it moves uniformly and rectilinearly.

Advice

In the case of uniform motion, there are no complications: you just need to find the ratio of the distance to the time for which it was overcome. In this case, the average and instantaneous velocity of the body are equal. If the motion is not constant, then in this case it is necessary to find out the magnitude of the acceleration and to determine the instantaneous velocity at each particular instant of time. When moving vertically, it is necessary to take into account the effect of acceleration of gravity. The instantaneous speed of the car can be determined using a radar or speedometer. It should be borne in mind that movement in some sections of the path may take a negative value. In order to find the acceleration, you can use the accelerometer or make up the motion function and use the formula v = v0 + a • t. If the displacement starts from the resting state, then v0 = 0. In calculations, it is necessary to take into account the fact that when the body is decelerated (decreasing speed), the acceleration will be a minus sign. If the object makes a free fall, the instantaneous speed of its movement is calculated by the formula v = g • t. In this case, the initial velocity is also 0.