Among the "eternal" themes of the school program in physicssection "fluctuations", perhaps the most nostalgic - it is always remembered with some kind of warm sadness. Hardly anyone at least, remembering this topic, does not see, in the first place, a tick-tick, tick ... pendulum-the "most serious" device from the physics room. True, laboratory pendulums do not "tick", but their classic medieval appearance is always said, swaying, their eternal tick-so, tick ... "do not think about seconds down". And the task for these unpretentious devices is to show clearly what it is - fluctuations.
We know the world and see how much it meansaround us is such a simple and uncomplicated action. The oscillation is Foucault's pendulum, and the clock, and electricity, radio, TV, sound from the speaker, and the favorite cell phone is a whole cluster of oscillatory systems. Well, well, let's remember what was taught in school - the amplitude of oscillations, formulas, graphics. So, the hesitation ... but what is it?
All that surrounds us is "material points"which, for some reason, does not sit still. In this chaos of a variety of movements, vibrations are a process in which a material point, sometimes the system says, always returns to a position of equilibrium if it repeatedly deviates from it. In this case, the magnitude of the maximum deviation from the equilibrium point is called the amplitude of the oscillations. The best device for demonstrating mechanical oscillations, of course, is an old, kind pendulum-a load (ball, disk or rod) suspended on a string. Fix it motionless - and here is the state of balance. Take the load aside and release what you see? Correctly, he will start his "tick-to-do": return to the equilibrium position, deviate to the other side, then again return to the equilibrium position. If the pendulum does not interfere, then he, restless, will again turn aside ... and so continuously, while, due to the force of friction, he still does not stop.
So it was customary that any object havingmass, size and other distinctive features, necessarily contains a set of characteristics by which it is possible to unambiguously describe this "material point" so that its behavior from interaction with the environment is predictable, logical and understandable. These characteristics of the pendulum are the amplitude of the oscillations and the period. Other frequently used parameters are derived from the original ones, they are their organic part (phase) or the result of additional calculations (frequency).
The next step in exploring the fascinating worldoscillations - the simplest experiment to determine the parameters of our object - the pendulum. The device of the pendulum is nowhere simpler-thread, ball, point of suspension. And how to find the amplitude of oscillations of such a pendulum? It's so simple that such an experience, as they say, and in the kitchen could be done. Everything is easy (within certain limits). The initial task: there is a pendulum suspended from the ceiling - a metal disk on the thread. We are interested in the amount of deviation of the disk from the equilibrium position. When the pendulum is stationary, we mark the equilibrium point on the wall, or on the paper screen installed behind it. Push the disc. The pendulum will begin to oscillate, and the shadow from the disc will "draw" the trajectory on the screen. Moving the wand (you can pencil) on the screen, we find the last point, when the shadow with oscillations in the extreme point closes our pointer, and make a mark. The distance from the point of equilibrium to the mark will be the amplitude of the oscillations of the pendulum. Is not it difficult? And who would doubt.
Of course, you can "modernize" the experimentelectronic bells and whistles with photosensors or use laser distance meters to measure up to some tempting figure after the decimal point, but nothing can change its essence - the greatest deviation of the pendulum from the equilibrium position has been measured, i.e. the amplitude is measured. In the experiment we have done, it is easy to find out one "secret" of the pendulum - its amplitude depends only on the initial conditions, i.e. in fact from the force of the first shock that disturbed the state of equilibrium, or the initial energy imparted to the oscillatory system, when the pendulum is deflected by some angle from the equilibrium position.