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yinghui95

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Number of posts : 223
Registration date : 2007-01-04

PostSubject: ICE SKATING   Thu May 17, 2007 3:39 pm

ICE SKATING
COME ON IN TO KNOW MORE ABOUT ICE SKATING


HISTORY

The exact time and process by which humans first learned to ice skate is not known, though archaeologists believe the activity was widespread. The convenience and efficiency of ice skating to cross large, icy areas is shown in archaeological evidence by the finding of primitive animal bone ice skates in places such as Russia, Scandinavia, Great Britain, the Netherlands, Germany, and Switzerland. The first recorded skates were found at the bottom of a lake in Switzerland and dated back to 3000BC. The runners were made from bones of cattle. They were ground down until they formed a flat gliding surface, and thongs tied them to the feet. And we need more info... [1]


When the great marsh that laps up against the northern walls of the city is frozen, large numbers of the younger crowd go there to play about on the ice... Others are more skilled at frolicking on the ice: they equip each of their feet with an animal's shin-bone, attaching it to the underside of their footwear; using hand-held poles reinforced with metal tips, which they periodically thrust against the ice, they propel themselves along as swiftly as a bird in flight or a bolt shot from a crossbow. But sometimes two, by accord, beginning far apart, charge each other from opposite directions and, raising their poles, strike each other with them. One or both are knocked down, not without injury, since after falling their impetus carries them off some distance and any part of their head that touches the ice is badly scratched and scraped. Often someone breaks a leg or an arm, if he falls onto it.



DO YOU KNOW HOW IT WORK?


Ice skating works because the metal blade at the bottom of the ice skate shoe can glide with very little friction over the surface of the ice. However, slightly leaning the blade over and digging one of its edges into the ice ("rockover and bite") gives skaters the ability to increase friction and control their movement at will. In addition, by choosing to move along curved paths while leaning their bodies radially and flexing their knees, skaters can use gravity to control and increase their momentum. They can also create momentum by pushing the blade against the curved track which it cuts into the ice. Skillfully combining these two actions of leaning and pushing ~ a technique known as "drawing" - results in what looks like effortless and graceful curvilinear flow across the ice.
Experiments show that ice has a minimum kinetic friction at −7C (19F), and many indoor skating rinks set their system to a similar temperature. The low amount of friction actually observed has been difficult for physicists to explain, especially at lower temperatures. On the surface of any body of ice at a temperature above about −20C (−4F), there is always a thin film of liquid water, ranging in thickness from only a few molecules to thousands of molecules. This is because an abrupt end to the crystalline structure is not the most entropically favorable possibility. The thickness of this liquid layer depends almost entirely on the temperature of the surface of the ice, with higher temperatures giving a thicker layer. However, skating is possible at temperatures much lower than −20C, at which there is no naturally occurring film of liquid.
When the blade of an ice skate passes over the ice, the ice undergoes two kinds changes in its physical state: an increase in pressure, and a change in temperature due to kinetic friction and the heat of melting. Direct measurements[2] show that the heating due to friction is greater than the cooling due to the heat of melting. Although high pressure can cause ice to melt, by lowering its melting point, the pressure required is far greater than that actually produced by ice skates. Frictional heating does lead to an increase in the thickness of the naturally occurring film of liquid, but measurements with an atomic force microscope have found the boundary layer to be too thin to supply the observed reduction in friction.


THE DANGERS!!!!!

The first main danger in ice skating is falling on the ice, which is dependent on the quality of the ice surface, the design of the ice skate, and the skill and experience of the skater. While serious injury is rare, a number of (short track) skaters have been paralyzed after a fall when they hit the boarding. An additional danger of falling is injury caused by the metal blades of the skater himself or other skaters.
The second and more serious danger is the chance of falling through the ice into the freezing water underneath when skating outdoors. This can lead to serious injury or death due to shock, hypothermia or drowning. It is often difficult or impossible for skaters to climb out of the water back onto the ice due to the ice repeatedly breaking, the skater being weighed down by skates and thick winter clothing, or the skater becoming disorientated under water and being unable to find the entry hole which can lead them to being trapped under the ice.


WHAT IS NEEDED?
ICE SKATES A TICK JACKET IS NEEDED FOR IT.
this is the photo of outdoor iceskating in australia.

SKILLS
SKATING SKILLS IS NEEDED BEFORE YOU TRY IT. YOUU WILL FALL DOWN IF YOU DO NOT KNOW THE SKILLS FOR IT.

HOPE THAT YOU ALL WILL LIKE IT:P
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