Acceleration – the physical concept characterizing speed of the movement of a material point. It is the vector size which direction coincides with the applied force, and the value is proportional to this force according to the second law of Newton.
Instruction
1. Acceleration shows increase of speed of a body in unit of time. As well as speed, it can be both a constant and a variable depending on type of the movement. The section of physics under the name kinematics is engaged in studying motion of bodies.
2. Physical bodies move on different trajectories and with various speed, for example, there is a rectilinear and curvilinear movement, rotary and oscillatory. In turn, rectilinear is uniform and uneven to equal or variable acceleration.
3. Movement of a body of the same distance for equal periods is called uniform. Acceleration at the same time is equal to zero. To calculate acceleration of the rectilinear non-uniform uniformly accelerated motion, it is necessary to use a formula: a = (v-v_0)/t, where v_0 and v – body speeds, respectively, at the beginning and the end of movement.
4. Such acceleration can be both positive, and negative, in the second case speak about the ravnozamedlenny movement. At variable acceleration it makes sense to find average acceleration which is defined as a derivative of function of speed, namely a ratio limit between increment of speed of ∆v and increment of time of ∆t which tends to zero: = v’ _t = lim _ (∆ t→0) ∆v / ∆ t.
5. The acceleration vector at the curvilinear movement has various directions as depends on a trajectory form. However it is optional to consider each site of a curve, it is enough to tell that in each case this part of a way represents a circle arch. Therefore the task comes down to definition of acceleration at uniform motion of a body on a circle: a = v \, where r is circle radius.
6. At rotation of a body around a motionless axis calculate angular acceleration which is equal to the first derivative angular speed on time: a = w’ _t, the module of angular speed is in number equal to an angle of rotation per unit of time.
7. The repeating rocking of a body in one and in another the parties is characteristic of oscillating motion. As an example it is possible to remember pendulums, molecules, parts of the working cars and so forth. Acceleration at such movement is changeable size. With the maximum amplitude of fluctuation it reaches the maximum, in a balance point it is zero.
8. The simplest type of such movement are harmonic oscillations. Acceleration in this case also submits to the harmonious law: a = - to w²\• xm • cos (w · t + φ _ 0), where: w – frequency of fluctuations, xm is the maximum amplitude, φ _ 0 – an initial phase of fluctuations.
9. The minus sign in this formula shows that the direction of acceleration is always opposite to shift. It means that according to the second law of Newton force forcing a body to make fluctuations is always directed towards balance of x=0.