These tricks, or analysis tools, are detailed in the following section. Learning to use these three terms correctly can be made much easier by learning a few tricks of the trade. Kinematics is the correct use of the parameters position, velocity, and acceleration to describe motion. Conversely, a positive acceleration means that the change in the velocity points in the positive direction. Both of these scenarios would result in a negative acceleration. For example, the velocity could be in the positive direction and the object slowing down or the velocity could be in the negative direction and the object speeding up. A negative acceleration means that the change in the velocity points in the negative direction. The algebraic sign of the acceleration depends on the coordinate system chosen to define the position. Since vfinal may be either positive, negative, or zero, and either larger, smaller, or the same as vinitial, the acceleration may be positive, negative, or zero. Thus, acceleration is measured in meters per second per second (m/s2).Īgain, this is actually the average acceleration of the object over the time interval Dt, but as the time interval becomes smaller and smaller, the value of this expression becomes closer and closer to the actual rate at which the velocity is changing at one particular instant of time. We will use the symbol r to designate position, and measure it in meters (m). Depending on the coordinate system chosen, the position of an object can be positive, negative, or zero. It doesn’t matter what you choose as a coordinate system, only that you explicitly choose one. Of course, choosing the zero at the location at which the object was dropped, the positive direction as down, and the scale in feet is also perfectly acceptable. Using this coordinate system, the position of the object could have been specified at any particular instant of time.

A coordinate system is comprised of a zero, a specified positive direction, and a scale.įor example, in the hypothetical experiment in which the object was dropped from shoulder height, a coordinate system could have been defined in which the zero position was at ground level, the positive direction was up, and the scale used was meters.

Without a specified coordinate system, position is a meaningless concept.

The position of an object is its location relative to a well-defined coordinate system at a particular instant of time.

Formulas cinematicas