- published: 11 Aug 2014
- views: 7578
A gramophone record, commonly known as a phonograph record (in American English), vinyl record (in reference to vinyl, the material most commonly used after about 1950), or colloquially, a record, is an analog sound storage medium consisting of a flat disc with an inscribed, modulated spiral groove. The groove usually starts near the periphery and ends near the center of the disc. Phonograph records are generally described by their diameter in inches (12-inch, 10-inch, 7-inch, etc.), the rotational speed at which they are played ("33⅓ r.p.m.", "78", "45", etc.), their time capacity ("Long Playing"), their reproductive accuracy, or "fidelity", or the number of channels of audio provided ("Mono", "Stereo", "Quadraphonic", etc.).
Gramophone records were the primary medium used for music reproduction for most of the 20th century, replacing the phonograph cylinder, with which it had co-existed, by the 1920s. By the late 1980s, digital media had gained a larger market share, and the vinyl record left the mainstream in 1991. However, they continue to be manufactured and sold in the 21st century. The vinyl record regained popularity by 2008, with nearly 2.9 million units shipped that year, the most in any year since 1998 and the format has continued to slowly regain popularity. They are especially used by DJs and audiophiles for many types of music. As of 2012, vinyl records continue to be used for distribution of independent and alternative music artists. More mainstream pop music releases tend to be mostly sold in compact disc or other digital formats, but have still been released in vinyl in certain instances.
Revolutions per minute (abbreviated rpm, RPM, r/min, or r·min−1) is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis. It is used as a measure of rotational speed of a mechanical component.
Standards organizations generally recommend the symbol r/min, which is more consistent with the general use of unit symbols. This is not enforced as an international standard. In French for example, tr/mn (tours par minute) is commonly used, and the German equivalent reads U/min (Umdrehungen pro Minute).
According to the International System of Units (SI), rpm is not a unit. This is because Revolutions is a semantic annotation rather than a unit. The annotation is instead done in the subscript of the formula sign if needed. Because of the measured physical quantity, the formula sign has to be f for (rotational) frequency and ω or Ω for angular velocity. The corresponding basic SI unit is s−1 or Hz. When measuring angular speed, rad·s−1 can also be used as unit.
Não fale de amor
Não diga bobagem
Não prometa aquilo que não vai cumprir
Eu já sei de cór toda essa viagem
E sei que não é fácil decidir
Mas seja o que for
Tome cuidado
Aparetemente não faz mal
Brincar de amor
Mas é complicado
E qualquer erro pode ser fatal
Não fale demais
Não se desespere
Tudo tem a hora e o lugar
Não volte atrás
Agora, espere
Procure aprender como se faz.