Sound Vibrations and Waves 
Introduction The term "sound" has two senses: first in the subjective sense is used to describe the sensation experienced by an observer when the terminations the auditory nerve receives a stimulus, but also used in the objective sense to describe the waves produced by compression of air that can stimulate the auditory nerve of an observer. Pendulum In physics is given the name of an object that pendulum could swing freely about an axis. This definition suffers strong restrictions when you want to characterize what we call ideal pendulum in physics. It is actually an imaginary model of a pendulum that would consist of a particle that is suspended by a thread deformable and weightless and frictionless oscillating one. Obviously we can not build an ideal pendulum, but try to approach its best, using in a small body and long thin wire, avoiding contact as much as possible.
Our pendulum will have a body of mass m and a length l measured from the suspension point 0 to the center of gravity. We will take as the equilibrium position to the vertical which passes through O. When the pendulum is in one of its extreme positions, the thread makes an angle to the position of equilibrium. This angle is called amplitude.
The pendulum makes a complete swing when it happens twice in a row at the same point of his career in the same direction.
isochronous LAW OF PENDULUM
formulas of the period and frequency of the pendulum and suggest that these quantities depend only on the length of the wire and the acceleration of gravity. 1) The period T of a pendulum is independent of the pendulum mass: Whatever the value of the pendulum mass "m", the term "T" is constant (For the same wire length "l" and in the same place on earth).
2) The period T of a pendulum is independent of the amplitude of the oscillation: This is true for maximum angles of oscillation "to" less than 15 °, as already cited, since for larger angles the approximation made differs greater than 1%. If the same spot on earth (g = constant) are measured periods of two pendulums of different lengths l1 and l2 is: If a single pendulum ("l" = constant) was measured oscillation periods in two different points acceleration of gravity g1 and g2, is:
The vibration waves come and go (often also known as oscillatory movement) of a pendulum that describes a small arc is called simple harmonic motion. The bob of a pendulum, full of sand, which is shown in Figure 1, is simple harmonic motion on a conveyor belt. When the band does not move (Fig. A), the loose sand draw a line. The most interesting is that when the conveyor belt moves at constant speed (Figure B), leaving the sand draws a special curve called sine wave or sinusoid.
Size Also a counterweight to this fixed to a spring, which has vertical simple harmonic motion, describes a sine curve (Fig. 2), which is a graphical representation of a wave. As with a water wave, the high points of a sine wave are called crests, and low spots, valleys. The dotted straight line represents the "initial" or "midpoint" of vibration. Applies the term broadly to indicate the distance from midpoint to the crest (or trough) of the wave. Thus the amplitude is equal to the maximum displacement from equilibrium.
Wavelength Wavelength is the distance from the top a ridge to the top of the next ridge. Also, wavelength is the distance between any two successive identical parts of the wave. The wavelengths of the waves on the beach is measured in meters, those ripples on a pond, in centimeters, and light, in thousandths of millionths of a meter (nanometers). The repetition rate of vibration is described by frequency. The frequency of a swinging pendulum, or a fixed object on a spring, indicates the number of oscillations or vibrations made by a certain time (which is usually a second). A complete swing back and forth is a vibration. If done in a second frequency is a vibration per second. If a second, there are two vibrations, the frequency is two vibrations per second. The unit of frequency
The unit of frequency called hertz (Hz), in honor of Huiriche Hertz, who proved the existence of radio waves in 1886. One vibration per second is 1 Hz, two vibrations per second is 2 hertz, etc. The higher frequencies are measured in kilohertz (kHz, thousands of hertz) and even higher frequencies are measured yet megahertz (MHz, millions of hertz) or gigahertz (GHz, billions of hertz). The period of a vibration
The period of a vibration or a wave is the time it takes to complement a vibration. If you know the frequency of an object, you can determine its period, and vice versa. For example, imagine a pendulum makes two oscillations in a second. Its vibration frequency is 2 Hz time required to complete a vibration, the period is 1 / 2 second. Or, if the vibration frequency is 3 Hz, then the period is 1 / 3 of a second. The frequency and period are reciprocals of each other:
Wave Motion
The type of movement characteristic of waves is called wave motion. Its essential property is that it involves a mass transport from one point to another. Thus, there is a domino or a set of conditions moving forward from the starting point at the end, on the contrary, their individual movement does not reach more than a few centimeters. The same happens in the wave that is generated on the surface of a lake or produced in a string by vibrating one end. In all cases the constituent particles of the medium move relatively little from its equilibrium position. What are advancing and progressing them, but the disturbance that passed each other. The wave motion is only a transport of energy and momentum. Speed \u200b\u200bof a wave
The speed of periodic wave motion related to the frequency and wavelength of waves. We understand this if we imagine the simple cas wave in water (Fig. 3). If we set eyes on a stationary point of the water surface and observe the waves pass through, we could measure how much time elapses between the arrival of a crest and the arrival of the next crest (the wavelength). We know that speed is defined as a distance divided by time. In this case, the distance is one wavelength and time-period, so that the wave speed = wavelength / period. For example, if the wavelength is 10 meters and the time between peaks, at a point on the surface, is 0.5 seconds, the wave travels 10 meters in 0.5 seconds, and speed is 10 meters divided enters 0.5 seconds or 20 meters per second.
As the period is equal to the inverse of the frequency, wave speed formula 0 wavelength / period is also written as: Fast wave length and frequency =
This relationship is valid for all kinds of waves , whether water, sound or light. Transverse waves environmental disturbance occurs in the direction perpendicular to the propagation. In the waves produced in the surface particles vibrate from top to bottom and vice versa, while the wave motion in the plane perpendicular progresses. The same is true in the case of a rope, each point vibrates vertically, but the disturbance moves in the direction of the horizontal line. Both are transverse waves.
Longitudinal waves Longitudinal waves: are those where the direction in which the disturbance is traveling parallel to the direction of propagación.Pero to fix ideas, consider a spring in which one end is moved so compress or stretch the spring horizontally as shown in Figure 4. Consider what happens when you compress the spring. At that time the coils that are in the end will be pushed (1), so that its density increases beyond normal. Then he begins to recede (2), at this point turns density begins to decrease. This difference in density of turns that is generated in the spring is a disturbance that propagates through the spring, but you can see that the direction of propagation is the same as that in which I produce the disturbance.
Standing waves Standing waves are those waves in which certain points of the wave called nodes, are motionless. In this type of waves, the positions where the amplitude is maximal are known as antinodes, which are formed at the midpoints between two nodes. Standing waves are produced by the interference. When two waves of equal amplitude, wavelength and speed in the opposite direction to move through a medium form waves.
For example, if a wall is attached to the end of a rope and shake the other end up and down, the waves are reflected on the wall and return in reverse. Assuming that the reflection is perfectly efficient, the reflected wave is half wavelength lags behind the initial wave. Interference occurs between waves and the resultant displacement at any point and time is the sum of the displacements corresponding to the incident wave and the reflected wave. At points where a crest of the wave incident coincides with a valley of the mirror, there is no movement, these points are called nodes. Halfway between two nodes, the two waves are phase, ie peaks coincide with peaks and valleys with valleys on these points, the resulting wave amplitude is twice that of the incident wave, so the string is divided into sections by the nodes a wavelength. Between nodes (which do not advance through the string), the string vibrates transversely. waves are formed on the strings of musical instruments that are plucked, beat or played with a bow and in the air in an organ pipe and a bottle of soda when we blow on his mouth. You can create waves in both transverse waves as in the longitudinal.
