A skateboard is a type of sports equipment used for skateboarding. They are usually made of a specially designed 7-8 ply maple plywood deck and polyurethane wheels attached to the underside by a pair of skateboarding trucks.
The skateboarder moves by pushing with one foot while the other foot remains balanced on the board, or by pumping one's legs in structures such as a bowl or half pipe. A skateboard can also be used by simply standing on the deck while on a downward slope and allowing gravity to propel the board and rider. If the rider's leading foot is their right foot, they are said to ride "goofy;" if the rider's leading foot is their left foot, they are said to ride "regular." If the rider is normally regular but chooses to ride goofy (or vice versa), they are said to be riding in "switch". A skater is typically more comfortable pushing with their back foot; choosing to push with the front foot is commonly referred to as riding "mongo", and has negative connotations of style and effectiveness in the skateboarding community.
Since the early 2000s electric skateboards have appeared. These no longer require the propelling of the skateboard by means of the feet; rather an electric motor propels the board, fed by an electric battery.
There is no governing body that declares any regulations on what constitutes a skateboard or the parts from which it is assembled. Historically, the skateboard has conformed both to contemporary trends and to the ever-evolving array of stunts performed by riders/users, who require a certain functionality from the board. The board shape depends largely upon its desired function. Longboards are a type of skateboard with longer wheelbase and larger, softer wheels.
The two main types of skateboards are the longboard and the shortboard. The shape of the board is also important: the skateboard must be concaved to perform tricks. Longboards are usually faster and are mostly used for cruising and racing, while shortboards are mostly used for doing tricks and riding in skateparks.Affect may refer to:
Affect (education)
Affect (linguistics), attitude or emotion that a speaker brings to an utterance
Affect (philosophy)
Affect (psychology), the experience of feeling or emotion
Affect display, signs of emotion, such as facial expression, vocalization, and posture
Affect theory
Affective science, the scientific study of emotion
Affective computing, an area of research in computer science aiming to understand the emotional state of users
Reduced affect display, a.k.a. emotional blunting or affective flattening, a reduction in emotional reactivity
Pseudobulbar affect, a.k.a. labile affect, the unstable display of emotion
Affect (rhetoric), the responsive, emotional feeling that precedes cognition
Affected accent; see Accent (sociolinguistics)
Affect (company), a defunct Japanese video game developerA planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and – according to the International Astronomical Union but not all planetary scientists – has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Apart from Earth itself, five planets in the Solar System are often visible to the naked eye. These were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, incorporating a number of disparate objects. In 2006, the International Astronomical Union (IAU) officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of planetary mass based on where or what they orbit. Although eight of the planetary bodies discovered before 1950 remain "planets" under the current definition, some celestial bodies, such as Ceres, Pallas, Juno and Vesta (each an object in the solar asteroid belt), and Pluto (the first trans-Neptunian object discovered), that were once considered planets by the scientific community, are no longer viewed as planets under the current definition of planet.
The planets were thought by Ptolemy to orbit Earth in deferent and epicycle motions. Although the idea that the planets orbited the Sun had been suggested many times, it was not until the 17th century that this view was supported by evidence from the first telescopic astronomical observations, performed by Galileo Galilei. About the same time, by careful analysis of pre-telescopic observational data collected by Tycho Brahe, Johannes Kepler found the planets' orbits were elliptical rather than circular. As observational tools improved, astronomers saw that, like Earth, each of the planets rotated around an axis tilted with respect to its orbital pole, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the other planets share characteristics such as volcanism, hurricanes, tectonics, and even hydrology.
Planets in the Solar System are divided into two main types: large low-density giant planets, and smaller rocky terrestrials. There are eight planets in the Solar System according to the IAU definition. In order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites, the two exceptions being Mercury and Venus.
Several thousands of planets around other stars ("extrasolar planets" or "exoplanets") have been discovered in the Milky Way. As of 1 September 2021, 4,834 known extrasolar planets in 3,572 planetary systems (including 795 multiple planetary systems), ranging in size from just above the size of the Moon to gas giants about twice as large as Jupiter, have been discovered, out of which more than 100 planets are the same size as Earth, nine of which are at the same relative distance from their star as Earth from the Sun, i.e. in the circumstellar habitable zone. On 20 December 2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A 2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way.
Around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone.Prevention may refer to:
| תאריך המענק | 2016 |
|---|
| שפה מקורית | ???core.languages.en_GB??? |
|---|