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top 10 words in brain distribution (in article): species animal horse male female wear time breed record food |
top 10 words in brain distribution (in article): energy power form muscle produce human time bone design structure |
top 10 words in brain distribution (not in article): bird egg card fish cat service information company kill ant |
top 10 words in brain distribution (not in article): cell fuel engine vehicle church gas body car wheel oil |
times more probable under horse 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under hammer (words not in the model) | |
The horse'" ("Equus ferus caballus") is a hoofed (ungulate) mammal, a subspecies of one of seven extant species of the family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today. Humans began to domesticate horses around 4000 BC, and their domestication is believed to have been widespread by 3000 BC; by 2000 BC the use of domesticated horses had spread throughout the Eurasian continent. Although most horses today are domesticated, there are still endangered populations of the Przewalski's Horse, the only remaining true wild horse, as well as more common feral horses which live in the wild but are descended from domesticated ancestors. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior. Horses are anatomically designed to use speed to escape predators, and have a well-developed sense of balance and a strong fight-or-flight instinct. Related to this need to flee from predators in the wild is an unusual trait: horses are able to sleep both standing up and lying down. Female horses, called mares, carry their young for approximately 11 months, and a young horse, called a foal, can stand and run shortly following birth. Most domesticated horses begin training under saddle or in harness between the ages of two and four. They reach full adult development by age five, and have an average lifespan of between 25 and 30 years. Horse breeds are loosely divided into three categories based on general temperament: spirited "hot bloods" with speed and endurance; "cold bloods," such as draft horses and some ponies, suitable for slow, heavy work; and "warmbloods," developed from crosses between hot bloods and cold bloods, often focusing on creating breeds for specific riding purposes, particularly in Europe. There are over 300 breeds of horses in the world today, developed for many different uses. Horses and humans interact in many ways, not only in a wide variety of sport competitions and non-competitive recreational pursuits, but also in working activities including police work, agriculture, entertainment, assisted learning and therapy. Horses were historically used in warfare. A wide variety of riding and driving techniques have been developed, using many different styles of equipment and methods of control. Many products are derived from horses, including meat, milk, hide, hair, bone, and pharmaceuticals extracted from the urine of pregnant mares. Humans provide domesticated horses with food, water and shelter, as well as attention from specialists such as veterinarians and farriers. Biology. Horse anatomy is described by a large number of specific terms, as illustrated by the chart to the right. Specific terms also describe various ages, colors and breeds. Age. Depending on breed, management and environment, the domestic horse today has a life expectancy of 25 to 30 years. It is uncommon, but a few animals live into their 40s and, occasionally, beyond. The oldest verifiable record was "Old Billy," a 19th-century horse that lived to the age of 62. In modern times, Sugar Puff, who had been listed in the Guinness Book of World Records as the world's oldest living pony, died in 2007, aged 56. Regardless of a horse's actual birth date, for most competition purposes an animal is considered a year older on January 1 of each year in the northern hemisphere and August 1 in the southern hemisphere. The exception is in endurance riding, where the minimum age to compete is based on the animal's calendar age. A very rough estimate of a horse's age can be made from looking at its teeth. The following terminology is used to describe horses of various ages: In horse racing, the definitions of colt, filly, mare, and stallion may differ from those given above. In the UK, Thoroughbred horse racing defines a colt as a male less than five years old, and a filly as a female less than five years old. In the USA, both Thoroughbred racing and harness racing defines colts and fillies as four years old and younger. Size. The English-speaking world measures the height of horses in hands, abbreviated "h" or "hh," for "hands high," measured at the highest point of an animal's withers, where the neck meets the back, chosen as a stable point of the anatomy, unlike the head or neck, which move up and down; one hand is. Intermediate heights are defined by hands and inches, rounding to the lower measurement in hands, followed by a decimal point and the number of additional inches between 1 and 3. Thus a horse described as "15.2 h," is 15 hands, 2 inches in height. The size of horses varies by breed, but can also be influenced by nutrition. The general rule for cutoff in height between what is considered a horse and a pony at maturity is 14.2 hands. An animal 14.2 h or over is usually considered to be a horse and one less than 14.2 h a pony. However, there are exceptions to the general rule. Some breeds which typically produce individuals both under and over 14.2 h are considered horses regardless of their height. Conversely, some pony breeds may have features in common with horses, and individual animals may occasionally mature at over 14.2 h, but are still considered to be ponies. The distinction between a horse and pony is not simply a difference in height, but takes account of other aspects of "phenotype" or appearance, such as conformation and temperament. Ponies often exhibit thicker manes, tails and overall coat. They also have proportionally shorter legs, wider barrels, heavier bone, shorter and thicker necks, and short heads with broad foreheads. They often have calmer temperaments than horses and also a high level of equine intelligence that may or may not be used to cooperate with human handlers. In fact, small size, by itself, is sometimes not a factor at all. While the Shetland pony stands on average 10 hands high, the Falabella and other miniature horses, which can be no taller than, the size of a medium-sized dog, are classified by their respective registries as very small horses rather than as ponies. Light riding horses such as Arabians, Morgans, or Quarter Horses usually range in height from 14 to 16 hands and can weigh from. Larger riding horses such as Thoroughbreds, American Saddlebreds or Warmbloods usually start at about 15.2 hands and often are as tall as 17 hands, weighing from. Heavy or draft horses such as the Clydesdale, Belgian, Percheron, and Shire are usually at least 16 to 18 hands high and can weigh from about. The largest horse in recorded history was probably a Shire horse named Sampson, who lived during the late 1800s. He stood 21.2½ hands high, and his peak weight was estimated at. The current record holder for the world's smallest horse is Thumbelina, a fully mature miniature horse affected by dwarfism. She is tall and weighs. Colors and markings. Horses exhibit a diverse array of coat colors and distinctive markings, described with a specialized vocabulary. Often, a horse is classified first by its coat color, before breed or | A hammer'" is a tool meant to deliver an impact to an object. The most common uses are for driving nails, fitting parts, and breaking up objects. Hammers are often designed for a specific purpose, and vary widely in their shape and structure. Usual features are a handle and a head, with most of the weight in the head. The basic design is hand-operated, but there are also many mechanically operated models for heavier uses. The hammer is a basic tool of many professions, and can also be used as a weapon. By analogy, the name "'hammer'" has also been used for devices that are designed to deliver blows, e.g. in the caplock mechanism of firearms. History. The use of simple tools dates to about 2,400,000 BCE when various shaped stones were used to strike wood, bone, or other stones to break them apart and shape them. Stones attached to sticks with strips of leather or animal sinew were being used as hammers by about 30,000 BCE during the middle of the Paleolithic Stone Age. Its archeological record means it is perhaps the oldest human tool known. Designs and variations. The essential part of a hammer is the head, a compact solid mass that is able to deliver the blow to the intended target without itself deforming. The opposite side of a ball as in the ball-peen hammer and the cow hammer. Some upholstery hammers have a magnetized appendage, to pick up tacks. In the hatchet the hammer head is secondary to the cutting edge of the tool. In recent years the handles have been made of durable plastic or rubber. The hammer varies at the top, some are larger than others giving a larger surface area to hit different sized nails and such, Mechanically-powered hammers often look quite different from the hand tools, but nevertheless most of them work on the same principle. They include: In professional framing carpentry, the hammer has almost been completely replaced by the nail gun. In professional upholstery, its chief competitor is the staple gun. Hammer as a force amplifier. A hammer is basically a force amplifier that works by converting mechanical work into kinetic energy and back. In the swing that precedes each blow, a certain amount of kinetic energy gets stored in the hammer's head, equal to the length "D" of the swing times the force "f" produced by the muscles of the arm and by gravity. When the hammer strikes, the head gets stopped by an opposite force coming from the target; which is equal and opposite to the force applied by the head to the target. If the target is a hard and heavy object, or if it is resting on some sort of anvil, the head can travel only a very short distance "d" before stopping. Since the stopping force "F" times that distance must be equal to the head's kinetic energy, it follows that "F" will be much greater than the original driving force "f" — roughly, by a factor "D" "d". In this way, great strength is not needed to produce a force strong enough to bend steel, or crack the hardest stone. Effect of the head's mass. The amount of energy delivered to the target by the hammer-blow is equivalent to one half the mass of the head times the square of the head's speed at the time of impact ([Formula 1]). While the energy delivered to the target increases linearly with mass, it increases geometrically with the speed (see the effect of the handle, below). High tech titanium heads are lighter and allow for longer handles, thus increasing velocity and delivering more energy with less arm fatigue than that of a steel head hammer of the same weight. As hammers must be used in many circumstances, where the position of the person using them cannot be taken for granted, trade-offs are made for the sake of practicality. In areas where one has plenty of room, a long handle with a heavy head (like a sledge hammer) can deliver the maximum amount of energy to the target. But clearly, it's unreasonable to use a sledge hammer to drive upholstery tacks. Thus, the overall design has been modified repeatedly to achieve the optimum utility in a wide variety of situations. Effect of the handle. The handle of the hammer helps in several ways. It keeps the user's hands away from the point of impact. It provides a broad area that is better-suited for gripping by the hand. Most importantly, it allows the user to maximize the speed of the head on each blow. The primary constraint on additional handle length is the lack of space in which to swing the hammer. This is why sledge hammers, largely used in open spaces, can have handles that are much longer than a standard carpenter's hammer. The second most important constraint is more subtle. Even without considering the effects of fatigue, the longer the handle, the harder it is to guide the head of the hammer to its target at full speed. Most designs are a compromise between practicality and energy efficiency. Too long a handle: the hammer is inefficient because it delivers force to the wrong place, off-target. Too short a handle: the hammer is inefficient because it doesn't deliver enough force, requiring more blows to complete a given task. Recently, modifications have also been made with respect to the effect of the hammer on the user. A titanium head has about 3% recoil and can result in greater efficiency and less fatigue when compared to a steel head with about 27% recoil. Handles made of shock-absorbing materials or varying angles attempt to make it easier for the user to continue to wield this age-old device, even as nail guns and other powered drivers encroach on its traditional field of use. War hammers. The concept of putting a handle on a weight to make it more convenient to use may well have led to the very first weapons ever invented. The club is basically a variant of a hammer. In the Middle Ages, the war hammer became popular when edged weapons could no longer easily penetrate some forms of armour. Symbolic hammers. The hammer, being one of the most used tools by "Homo sapiens", has been used very much in symbols and arms. In the Middle Ages it was used often in blacksmith guild logos, as well as in many family symbols. The most recognised symbol with a hammer in it is the Hammer and Sickle, which was the symbol of the former Soviet Union. The hammer in this symbol represents the industrial working class (and the sickle the agricultural working class). The hammer is used in some coat of arms in (former) socialist countries like East Germany. In Norse Mythology, Thor, the god of thunder and lightning, wields a hammer named Mjolnir. Many artifacts of decorative hammers have been found leading many modern practitioners of this religion to often wear reproductions as a sign of their faith. |