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Jumping
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Jumping or leaping is a form of locomotion or movement in which an organism propels itself through the air along a ballistic trajectory. Jumping can be distinguished from running, galloping and other gaits in which the entire body is temporarily airborne by the relatively long duration of the aerial phase and high angle of initial launch.
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Encyclopedia
Jumping or leaping is a form of locomotion or movement in which an organism propels itself through the air along a ballistic trajectory. Jumping can be distinguished from running, galloping and other gaits in which the entire body is temporarily airborne by the relatively long duration of the aerial phase and high angle of initial launch. Some animals, such as the kangaroo, use jumping, more commonly called hopping in this instance, as their primary form of locomotion, while others, such as frogs, use it only as a way to escape from predators.
Physics of jumping
All jumping is governed by basic physical laws of ballistic trajectories - once the animal has completely launched itself from the substrate, it will traverse a parabolic path determined by the launch angle, with launch angle and initial launch velocity determining distance, duration, and height of the jump. Maximum jump distance occurs at a launch angle of 45 degrees, but an animal can be within a range of 35-55 degrees and still achieve 90% of maximal distance.
A jump can be initiated when the animal is either moving or stationary. In a jump from stationary (a 'standing jump'), the animal is initially stationary, and all of the work done to accelerate the body through launch until takeoff is achieved is done in a single movement. The muscles do a certain amount of physical work (adding kinetic energy to the system), resulting in the final kinetic energy of the body (which is proportional to velocity squared). The more work the muscles do, the greater the final speed, thus the shorter the time interval of the jump's propulsive phase. Work divided by time = power. The more power generated, the greater the jump distance or height will be. Many jumping animals have muscles optimized for power production (as opposed to optimization for force or velocity), as well as adaptations such as elastic elements to increase power output.
In a moving jump or 'running jump', the animal simply redirects its velocity, attempting to conserve as much momentum as possible to add to the jump distance. Because the total kinetic energy of the jumping animal is not solely due to the jump movement itself, as is the case in a standing jump, but rather the energy of the jump plus the prior energy of the body, animals can often jump farther and higher if they 'get a running start'. In some cases, the animal will simply move in a give direction until they lose contact with it, without any specific launch movements, such as when a person runs across a gap from an elevated launch area, or when a dolphin swims upwards until breaking the surface at a given angle and velocity.
Jumping requires applying force against a substrate, which will in turn generate a reactive force, propelling the animal into the launch. This can be accomplished by pushing off against the ground or the water. In the latter case, dolphins often display moving jumps, while Indian skitter frogs can execute a standing jump from water. Jumping is typically defined by an airborne phase after launch from a substrate with a path defined by ballistic formulae, so animals cannot 'jump' underwater, as the drag and buoyancy overwhelm the influence of gravity. Similarly, while a bird can jump into the air in order to initiate flight, no movement it performs once airborne can be considered 'jumping'.
Anatomy
Animals use a wide variety of anatomical adaptations for jumping. These adaptations are exclusively concerned with the launch, as any post-launch method of extending range or controlling the jump must use aerodynamic forces, and thus is considered gliding.
Aquatic species rarely display any particular specializations for jumping. Those which are good jumpers usually are primarily adapted for speed, and execute moving jumps by simply swimming to the surface at a high velocity. A few primarily aquatic species which can jump while on land, such as mud skippers, do so via a flick of the tail.
In terrestrial animals, the primary propulsive organ is the legs, though a few species use their tails. Typical characteristics of jumping species include long legs, large leg muscles, and additional limb elements. Long legs benefit by increasing the time and distance over which the animal can push against the substrate, thus allowing more power and faster, farther jumps. Large leg muscles can generate greater forces, resulting in improved jumping performances. Many jumping animals have not only elongated the normal leg elements, but have also elongated other parts of the limb, such as foot and ankle bones, effectively adding more segments to the limb and even more length. Frogs are an excellent example of all three trends: frog legs can be nearly twice the body length, leg muscles may account for up to 20% of body weight, and they have not only lengthened the foot, shin and thigh, but extended the ankle bones into another limb joint and similarly extended the hip bones and gained mobility at the sacrum for a second 'extra joint'. As a result, frogs are the undisputed champion jumpers of vertebrates, leaping over 50 body lengths, more than 8 feet.
Grasshoppers are known to use elastic energy storage in order to increase jumping distance. As noted above, power output is the strongest determinant of jump distance, but the power that muscles can generate is limited due to physiological constraints of the muscles themselves to approximately 300 Watts per kg of muscle. In order to circumvent this power limitation, grasshopers anchor their legs via an internal 'catch mechanism' while their muscles stretch an elastic apodeme (similar to a vertebrate tendon). When the catch is released, the apodeme releases its energy all at once, at a much higher power output than muscles are capable of. This would be analogous to a human throwing an arrow by hand versus using a bow - the use of elastic storage allows muscles to operate closer to optimal, generating more force and doing more work, while the elastic element releases that work faster than muscles can. The use of elastic energy storage has been found in jumping mammals, as well as in frogs, and the increase in power can be from two- to seven-fold.
Tools
In some cases the height of a jump may be increased by using a trampoline, or, by converting horizontally directed velocity into vertically directed velocity by using a jump, such as a half pipe.
Classification
By foot transfer
One way to classify jumping is by the foot transfer. In this way, five basic jump forms are distinguished: jumping with 2 feet, hopping (jumping on 1 foot), leaping (jumping from one foot to another), assemble (jumping from 1 foot to 2) and sissonne (jumping from 2 feet to 1)
Leaping gaits
Leaping gaits, which are distinct from running gaits (see Locomotion), include cantering, galloping, and pronging.
- High jump, where the objective is to place a horizontal bar as high as possible and leap over it in one jump, preceded by a short run-up.
- Hurdling, a foot race where the track is covered with hurdles.
- Fierljeppen, similar to the long jump, but using a pole to cover the distance.
- Long jump, where the objective is to cover as large a horizontal distance as possible with one jump, preceded by a short run-up.
- Pole vault, in which is similar to the high jump, but competitors use a long flexible pole to cover a bigger height.
Sports
Animal sports
- Dog agility involves a handler directing a dog through various obstacles, including jumps.
- Hunter/Jumper involves a rider jumping a sequence of fences looking as good as possible and maintaining a good rhythm.
- Show jumping involves a rider jumping a sequence of fences as fast as they can, without getting faults.
External links
- - Dedicated to collecting pictures of people jumping in interesting locations around the world
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