A wave is a disturbance that propagates through space and time, usually with transference of energy. A mechanical wave is a wave that propagates or travels through a medium due to the restoring forces it produces upon deformation. There also exist waves capable of traveling through a vacuum, including electromagnetic radiation and probably gravitational radiation. Waves travel and transfer energy from one point to another, often with no permanent displacement of the particles of the medium (that is, with little or no associated mass transport); they consist instead of oscillations or vibrations around almost fixed locations.
Definition
Agreeing on a single, all-encompassing definition for the term wave is non trivial. A vibration can be defined as a back-and-forth motion around a reference value. However, a vibration is not necessarily a wave. Defining the necessary and sufficient characteristics that qualify a phenomenon to be called a wave is, at least, flexible.
The term is often understood intuitively as the transport of disturbances in space, not associated with motion of the medium occupying this space as a whole. In a wave, the energy of a vibration is moving away from the source in the form of a disturbance within the surrounding medium. However, this notion is problematic for a standing wave (for example, a wave on a string), where energy is moving in both directions equally, or for electromagnetic / light waves in a vacuum, where the concept of medium does not apply. There are water waves in the ocean; light waves from the sun; microwaves inside the microwave oven; radio waves transmitted to the radio; and sound waves from the radio, telephone, and voices.
Characteristics
Periodic waves are characterized by crests (highs) and troughs (lows), and may usually be categorized as either longitudinal or transverse. Transverse waves are those with vibrations perpendicular to the direction of the propagation of the wave; examples include waves on a string, and electromagnetic waves. Longitudinal waves are those with vibrations parallel to the direction of the propagation of the wave; examples include most sound waves.
When an object bobs up and down on a ripple in a pond, it experiences an orbital trajectory because ripples are not simple transverse sinusoidal waves.
Ripples on the surface of a pond are actually a combination of transverse and longitudinal waves; therefore, the points on the surface follow orbital paths.
All waves have common behavior under a number of standard situations. All waves can experience the following:
Reflection — change in wave direction after it strikes a reflective surface, causing the angle the wave makes with the reflective surface in relation to a normal line to the surface to equal the angle the reflected wave makes with the same normal line
Refraction — change in wave direction because of a change in the wave's speed from entering a new medium
Diffraction — bending of waves as they interact with obstacles in their path, which is more pronounced for wavelengths on the order of the diffracting object size
Interference — superposition of two waves that come into contact with each other (collide)
Dispersion — wave splitting up by frequency
Rectilinear propagation — the movement of light waves in a straight line also helpful for seismographs
Polarization
A wave is polarized if it oscillates in one direction or plane. A wave can be polarized by the use of a polarizing filter. The polarization of a transverse wave describes the direction of oscillation in the plane perpendicular to the direction of travel.
Longitudinal waves such as sound waves do not exhibit polarization. For these waves the direction of oscillation is along the direction of travel.this is very important
Examples of Wave
Ocean surface waves, which are perturbations that propagate through water
Radio waves, microwaves, infrared rays, visible light, ultraviolet rays, x-rays, and gamma rays, which make up electromagnetic radiation; can be propagated without a medium, through vacuum; and travel at 299 792 458 m/s in a vacuum
Sound — a mechanical wave that propagates through gases, liquids, solids and plasmas
Waves of traffics, that is, propagation of different densities of motor vehicles, and so forth, which can be modeled as kinematic waves, as first presented by Sir M.J. Lighthill
Seismic waves in earthquakes, of which there are three types, called S, P, and L
Gravitational waves, which are nonlinear fluctuations in the curvature of spacetime predicted by general relativity, but which have yet to be observed empirically
Inertial waves, which occur in rotating fluids and are restored by the Coriolis effect
This is my presentation about one of the most mysterious pheomenon in this whole universe, the Black Holes.
Supernova / hypernova explosion that occurred on a very huge and massive star forms smaller star called neutron star that has smaller size but very strong gravity that can make human flattened into ashes.
Because of the massive gravitation that the neutron star had, every material near the star and the star itself compressed into the core creating a hole in space-time. Once something (even light) passed it, it will never come back again, because the event of space-time will stop inside the black hole, even no one knows exactly what actually happened inside it.
The presentation contains further informations like:
Ga perlu banyak omong, langsung aja diliat gambar2 Missile milik Iran yang sangat ditakuti oleh Amerika dan Israel. Yang paling kecil aja daya ledaknya udah 9 Km !!!
Makin menjadi-jadi !!!
Sejil yang paling besar pada gambar diatas masih kalah sama Safir 1
Belum selesai
Iran masih rajin bikin missile lagi
Daya ledaknya Shahab 3 aja 2175 miles (= 3 500.323 2 Kilometer !!!)
Apalagi Shahab 5 yg besarnya 2x liapt Shahab 3, diperkirakan mencapai 5000 Km !!!!!!!!
Eh, ternyata ada yg lebih besar lagi, Shahab 6 dengan range ledakan sampai 10.000 KM !!!
Bisa hancur bumi kta bila yg satu ini diluncurkan :D :D
Ternyata Korea Utara jadi sumber beberapa missile Iran
When you saw the tittle, what is the first image that come from your mind? Almost of you think slug is the creature or animal like in this picture or snail without "house". Your imagination obviously correct, but now we don't talk about it. We will talk about another slug.
Slug (Mass)
The slug is a unit of mass associated with Imperial units. It is a mass that accelerates by 1 ft/s2 when a force of one pound-force (lbf) is exerted on it. Therefore a slug has a mass of 32.17405 pound-mass or 14.5939 kg.
(in terms of mass x acceleration) as
The slug is part of a subset of coherent units known as the gravitational foot-pound-second system (FPS), one of several such specialized systems of mechanical units developed in the late 19th and the 20th century. See the article poundal for an explanation of the problem such English units were introduced to solve.
The slug was first used in 1902 by Arthur Mason Worthington (1852–1916) in Dynamics of Rotation (OED), but it didn't see any significant use until decades later. A 1928 textbook says: "No name has yet been given to the unit of mass and, in fact, as we have developed the theory of dynamics no name is necessary. Whenever the mass, m, appears in our formulae, we substitute the ratio of the convenient force-acceleration pair (w/g), and measure the mass in lbs. per ft./sec.2 or in grams per cm./sec.2".
Another name for this unit in early literature is the geepound.
The unit slinch (derived from the words slug-inch ) is an inch version of the slug (1 slinch = 1 lbf·s2/in = 12 slugs).[5] The unit blob (bl) is also an inch version of the slug (1 lbf·s2/in).
