Speed in physics means the speed of movement of an object (material point) in space. This value can be different: linear, angular, medium, space, and even superlight. All existing varieties also include instantaneous speed. What is this quantity, what is its formula, and what actions are necessary for its calculation - this will be discussed in our article.
Instant Speed: Essence and Concept
Even a primary school student knows how to determine the speed of moving an object in a straight line: it is enough to divide the distance traveled by the time that was spent on such movement. However, it is worth remembering that the result obtained in this way allows you to judge the average value. If an object moves unevenly, then at certain parts of its path, the speed of movement can vary markedly. Therefore, sometimes such a value as instantaneous speed is required. It allows you to judge the speed of movement of a material point at any moment of movement.
Instant speed: calculation formula
This parameter is equal to the limit (indicated by limit, abbreviated lim) of the ratio of displacement (coordinate difference) to the period of time during which this change occurred, provided that this period of time tends to reach zero. This definition can be written as the following formula:
v = Δs / Δt as Δt → 0 or so v = lim Δt → 0 (Δs / Δt)
Note that the instantaneous velocity is a vector quantity. If the movement occurs in a straight line, then it changes only in magnitude, and the direction remains constant. Otherwise, the instantaneous velocity vector is directed tangentially with respect to the trajectory of movement at each point under consideration. What is the meaning of this indicator? Instantaneous speed allows you to find out what kind of movement the object will carry out per unit of time, if from the moment in question it moves uniformly and rectilinearly.
Advice
In the case of uniform movement, there are no difficulties: you just need to find the ratio of distance to time over which it was overcome by the object. In this case, the average and instantaneous velocity of the body are equal. If the movement is inconsistent, then in this case it is necessary to find out the magnitude of the acceleration and determine the instantaneous speed at each particular moment in time. When moving vertically, the influence of gravity acceleration should be taken into account . The vehicle’s instantaneous speed can be detected using a radar or speedometer. It should be borne in mind that the movement in some sections of the path can take a negative value.
In order to find acceleration, you can use the accelerometer or compose a motion function and use the formula v = v0 + a • t. If the displacement begins from a state of rest, then v0 = 0. In the calculations, it is necessary to take into account the fact that when the body is braked (speed decreases), the acceleration value will be with a minus sign. If an 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.