By the nature the motion can be uniform or variable. The main characteristic of the movement is the speed from which derivative is acceleration. Acceleration can be as constants, and to change in time.
Instruction
1. Uniform motion is calleditof movement at which the material point in any equal periods makes identical movements. Generally acceleration is called the size which shows how body speed quickly changes. At uniform motion the acceleration is equal to zero as speed at such movement a constant.
2. The variable movement is called the movement at which the speed of a body changes in time. The Ravnoperemenny movement is called the movement with acceleration, continuous in size. The acceleration vector at such movement is equal: a = ∆V / ∆ tispolzuya this formula, we will receive so-called average acceleration of a body for some period. To find acceleration of a body at present of time, it is necessary to find a limit of average acceleration at ∆t aspiring to 0. Let's designate change of a vector of speed as V2-V1= ∆ by V. Then acceleration is a limit to which the relation of change of a vector of speed of ∆V of time aspires at present to the corresponding period of ∆t at boundless reduction of a period. Acceleration can be both positive (the accelerated movement), and negative (the slowed-down movement). A special case of the rectilinear movement with continuous acceleration, that is the uniformly accelerated movement, is free fall of bodies.
3. Besides the progress described above there is a movement at which all points of a body make roundabout around an axis. By analogy with progress acceleration, angular acceleration of the ravnoperemenny movement is the size of change of speed in unit of time, only this speed is angular: j = ∆ ω/∆ tuskoreniye directed to a rotation axis that is is perpendicular to a vector of linear speed, is called centripetal and is on a formula: a=V^2/R=ω^2R, where V-linear speed, ω – the angular speed, R – radius.