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How Does ice skating work??

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johnnyd
689655.  Mon Mar 29, 2010 8:44 am Reply with quote

I am an applied physics student doing a thermal physics module and my lecturer pointed out that mathematically that a person could not excert enough force on the ground to create a thin film of water to skate on.
any ideas??

 
djgordy
689656.  Mon Mar 29, 2010 8:52 am Reply with quote

Quote:
(Professor Gabor) Somorjai's recent discoveries have explained why skaters and pucks slide on the ice. These new findings challenge long-held theories about why ice is slippery. In the past, scientists believed that either pressure or friction melted the ice, creating a water lubricant that allows skates and pucks to slide. Berkeley chemist Michel van Hove, a colleague of Somorjai's, has done calculations which show that skates and pucks do not generate enough pressure to instantly liquefy ice. Somorjai has discovered that ice has a "quasi-fluid layer" that coats the surface of ice and makes it slippery.


More info on the link to the whole article.
http://www.exploratorium.com/hockey/ice2.html

I still think that that invisible ice elves push you along but the scientific community is so narrow minded that I haven't, as yet, managed to get a grant to prove this.

 
RLDavies
689713.  Mon Mar 29, 2010 9:56 am Reply with quote

From DJGordy's link:
Quote:
Professor Somorjai's findings indicate that ice itself is slippery.

Quelle surprise.
From my extremely limited experience (one trip to the rink), ice skating consists of falling over every few seconds. Especially if there's a puddle nearby you can land in. Maybe somebody can do a study on the irresistible force of attraction exerted by puddles on skaters.

 
Neotenic
689720.  Mon Mar 29, 2010 10:17 am Reply with quote

This reminds me of the 'theoretically speaking, bees shouldn't be able to fly' thing.

If something which observably happens that theoretically shouldn't be possible, then that's a pretty reliable indicator that the theory is wrong.

 
Celebaelin
689730.  Mon Mar 29, 2010 10:51 am Reply with quote

You blow in one end and move your fingers up and down the outside, no, wait, that's how you play the clarinet.

 
CB27
689777.  Mon Mar 29, 2010 12:31 pm Reply with quote

Seems a strange question to vex the scientists.

We know that when you polish and buff a smooth surface it will become slippery.

We also know that water surface has a tension which allows it to "bend" the surface of the water into the shortest possible area.

It stands to reason that when left to freeze on it's own the surface tension of water will create as smooth a finish as is possible when frozen.

It's easier to skate with blades than with shoes on because they cut through the top layer of the ice, thus removing the buildup of rough slush you'd expect from rubing the ice.

 
gruff5
689851.  Mon Mar 29, 2010 2:24 pm Reply with quote

Neotenic wrote:
This reminds me of the 'theoretically speaking, bees shouldn't be able to fly' thing.

which is always misquoted.

Aerodynamicists actually said that a fixed-wing aircraft the size and wingspan of a bee couldn't fly. They, and we, are aware that bees flap their wings.

 
soup
689853.  Mon Mar 29, 2010 2:28 pm Reply with quote

gruff5 wrote:
Neotenic wrote:
This reminds me of the 'theoretically speaking, bees shouldn't be able to fly' thing.

which is always misquoted.

Aerodynamicists actually said that a fixed-wing aircraft the size and wingspan of a bee couldn't fly. They, and we, are aware that bees flap their wings.


Isn't the couldn't a misquote and it should be shouldn't?

 
Neotenic
689854.  Mon Mar 29, 2010 2:30 pm Reply with quote

Nope - it's the bee that shouldn't fly, but a bee-like fixed wing couldn't.

 
soup
689883.  Mon Mar 29, 2010 2:49 pm Reply with quote

Neotenic wrote:
Nope - it's the bee that shouldn't fly, but a bee-like fixed wing couldn't.


Seems rather definite, would they not have given the current understanding in their somewhere.

 
bobwilson
690045.  Mon Mar 29, 2010 11:36 pm Reply with quote

Nope - Neo is right. It's not a current understanding - it's an absolute understanding. A fixed wing bee couldn't and can't fly (at least on Earth).

 
bobwilson
690046.  Mon Mar 29, 2010 11:43 pm Reply with quote

johnnyd wrote:
I am an applied physics student doing a thermal physics module and my lecturer pointed out that mathematically that a person could not excert enough force on the ground to create a thin film of water to skate on.
any ideas??


This seems to be half a question

There's an implied statement that ice is itself not slippery. If ice is slippery then there's no requirement to create a thin film of water.

At least half the problem with models is asking the right questions.

At the risk of angering Samivel, can I suggest that someone who describes themself as "an applied physics student" should at least frame the question in a sensible manner? You could begin by stating (and preferrably demonstrating) that ice is itself not slippery.

 
grabagrannie
690117.  Tue Mar 30, 2010 6:11 am Reply with quote

Just how much pressure do you need to apply to make ice melt? Obviously, it depends on the temperature of the ice. But if we can assume that there is no point in cooling the ice much below the freezing point of water, then it would surely not take much pressure to make the ice melt. If the ice were at 0ļ, at normal atmospheric pressure, then any increase in pressure will take it into the liquid phase. A rough estimate of the pressure under a single blade for a 70 kg person would be about 50 N/cm^2 or 500,000 Pa.
That's not to say I don't believe the new research. If the old idea of what enabled skaters to skate were true, then, if the skater stood still, he would gradually sink into the ice and the water would refreeze over the blade, locking him in place, like that experiment with a piece of wire with weights on each end cutting through a piece of ice, but leaving it intact.

 
peteraugusts
691019.  Thu Apr 01, 2010 5:21 am Reply with quote

Ice-skating is a popular winter sport that is believed to date back thousands of years, when early types of ice-skates were made using the bones of animals instead of metal blades!

The reason ice-skating works is thanks to the unique characteristics of water and ice. If youíve ever tried to walk on a non-ice surface wearing skates, then you already know that other hard, smooth surfaces (like wood or cement) do not allow you to glide like you can when youíre on ice. The slippery surface of ice is one of the special properties of this cool solid, and it makes ice-skating possible! While scientists arenít sure of exactly what makes the surface of ice so slippery, most believe is either has to do with heat created from the friction of your skates, or the way that the units of water making up the outermost layer of ice donít stay as fully frozen as those below them.

Today, ice-skating is a recreational activity for many people, as well as the cornerstone of two different sports: figure skating and ice hockey!

 
Ion Zone
691275.  Thu Apr 01, 2010 3:30 pm Reply with quote

It is my experience that it doesn't work very well at all.

 

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