Wildguzzi.com
General Category => General Discussion => Topic started by: SmithSwede on January 10, 2017, 06:36:53 PM
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Seems like a simple question, right?
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Aren't you the MIT grad ? :laugh:
Dusty
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I'll bite - it isn't slippery in a solid state, it's the thin water layer that somehow forms on top under pressure that makes it slippery. Why that liquid layer of H2O forms is not totally 'clear' - get it? : )
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What Nic said. It is that perfect, thin layer or water that forms from the friction.
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What Nic said. It is that perfect, thin layer of water that forms from the friction.
I think it's from the friction and weight. The closer the ice is to the freezing point the more water is melting. Same for snow. That's why you need different wax for different temps. when skiing. Also, different length blades when speed skating. That is of course for the serious skaters.
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I think it's from the friction and weight. The closer the ice is to the freezing point the more water is melting. Same for snow. That's why you need different wax for different temps. when skiing. Also, different length blades when speed skating. That is of course for the serious skaters.
OO OO , what would you call a skating club made up of Guzzi riders ?
Dusty
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THIS is why:
https://www.youtube.com/watch?v=ZBrALhb8uiQ (https://www.youtube.com/watch?v=ZBrALhb8uiQ)
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I use Crampons when walking the dog these days, wiped out too many times on ice under snow cover.
my son the Hockey player plagiarized this,
A century and a half of scientific inquiry has yet to solve this one. It's clear that a thin layer of liquid water on top of solid ice causes the slipperiness. A fluid's mobility makes it difficult to walk on, even if the layer is thin. But there's no consensus as to why ice�unlike most other solids�has such a layer.
Scientists long reasoned that, since water has the unusual property of being less dense as a solid than as a liquid, its melting point can be lowered with an increase in pressure. While this is true, even the sharpest of skates raises the melting point by only a few degrees. The pressure theory doesn't hold water unless the ice is pretty warm already. Something else must be going on.
Some studies suggest that friction from a moving shoe, skate or tire causes the heat necessary to melt the ice beneath it. But what if the shoe isn't moving at all? A second theory proposes that ice inherently has a fluid layer, caused by the motion of surface molecules that have nothing above to bind to and so move around in search of stability. The slippery culprit may be a combination of these two theories.
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The Word of the Day is... ZAMBONI!!!
(http://zamboni.com/wp-content/gallery/evolution-of-the-machine/070_modelb.jpg)
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As a corollary to ice being less dense than liquid water (it floats), it has a lower melting point when under pressure. When compressed (by an ice skate blade, for example), a thin layer of ice instantly melts. It's actually a thin layer of water you're skating on, even at temperatures well below freezing.
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Water is weird stuff! A riding buddy used to be a science teacher. He described the anomalies once, but it was confusing enough I don't recall the whole story. I'll have to get him to go through it again. But what I remember was that ice doesn't necessarily float right off - it will stay submerged until the water around it gets to a certain temp. I've since noticed that ice cubes don't always come to the surface when I pour cold juice into the glass. They'll stay on the bottom for several minutes sometimes.
That's interesting data that pressure can instantly melt ice. I never knew that. Have to see what my friend has to say about that!
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Life on earth exists in part because water is more dense than ice. It is one of the four unique things about our planet. The others? We have an extremely large and relatively close moon, leading to substantial tides; we have an atmosphere that is neither too thin nor too dense; and we have a world that constantly rotates at just the right speed.
The combination of cold water sinking (but frozen water rising) and substantial tides means our oceans and larger bodies of fresh water are constantly turning over. This brings nutrients to the surface instead of allowing them to lay on the bottom with no oxygen or sunlight to break them down into useful components. Even further, the movement of the water gets accelerated by the rotation of the earth, creating huge currents. Finally, add in the floating ice at the poles (which conveniently reflects a substantial amount of light) and we have an extension of the warm and cold currents in the ocean into the thinner 'ocean' of air, carrying currents of heat, cold and moisture across the continents.
Eventually, this all leads to the ideal conditions for the rise of life, and the eventual and inevitable creation of Moto Guzzis and roads on which to ride them (Moto Guzzi content!).
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OO OO , what would you call a skating club made up of Guzzi riders ?
Dusty
Impossible?
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Impossible?
Not what we were looking for , but a good answer none the less :laugh:
Dusty
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OO OO , what would you call a skating club made up of Guzzi riders ?
Dusty
the Moto Guzzi Hockey team? A Curling club might be more appropriate ?
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When compressed (by an ice skate blade, for example), a thin layer of ice instantly melts. It's actually a thin layer of water you're skating on, even at temperatures well below freezing.
Right. It takes a lot of pressure to get the melting point to go substantially lower than 32F to allow skating to work, but there's a lot of pressure under a skate blade, like thousands of PSI. A good demonstration is to take a cinder block sized block of ice and suspend a heavy weight from it, using a thin piece of music wire looped around it. If you do it right, the wire will cut all the way through the ice, but the block will remain solid and unbroken, because the ice melts, and the water flows around the wire and refreezes.
If it's cold enough, ice skating stops being possible. I've never seen it in person, but I've read that it happens around -20F.
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I'm thinking that with a block of ice suspended by a loop of wire, the wire will gradually work its way through the block with the cut sealing itself back up, so that when the wire finally emerges from the top side, the block will fall (not in two pieces) and smash whatever is below it. This could provide the basis of a murder mystery!
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What Nic said. It is that perfect, thin layer or water that forms from the friction.
and/or pressure. (or other sources of heat.)
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Impossible?
Not what we were looking for , but a good answer none the less :laugh:
Dusty
"The Wholly Rolly Pollies"? "The Skidmark Skaters"?
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OO OO , what would you call a skating club made up of Guzzi riders ?
Dusty
Toronto Maple Leafs
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Toronto Maple Leafs
:shocked: Brutal!
To answer the OP: It's not that ice is or isn't slippery, it's that gravity sucks.
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Our team would be called the "Wild". To avoid a law suit we would have to change it to "just plain goofy".
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The correct answer of course is Cheapskates :laugh:
Dusty
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An important part of being slippery includes inertia. The only reason anything 'slips' on a low friction surface is inertia, Newton's first law or Galileo's law of inertia, which is that any object with mass that is in motion remains in motion until acted upon by an imbalanced force. And an object at rest remains at rest until acted upon by an imbalanced force.
Without friction or some other force, you would slide eternally... just like in space. You would not slow down, speed up, or change direction unless some force acted on you.
That's why we slide on ice or other low friction surfaces.
Interestingly, Newton's third law states that all forces come in pairs... no such thing as a single, lone force in the universe. They all come in pairs.
:laugh:
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The simplest correct answer it that it is slippery because it is lubricated.
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Ladies and gentlemen, take my advice. Pull down your pants and slide on the ice.
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The correct answer of course is Cheapskates :laugh:
Dusty
That pretty much hits the nail right on the head, Dusty. A more "tightwadly" (not really a word but fits) bunch I have yet to meet. Myself included.
As far as ice slipperiness goes a career of government studies could be had just examining the degrees of slipperiness because of snow content, ambient temperature etc. Best not to give those fools ideas to start, Oh wait the DOT has rooms full of these "experts" already doing just that.
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The correct answer of course is Cheapskates :laugh:
Dusty
I was thinking "Geezers on Ice".
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Yup, it's like why does a skidding tire out run a rolling tire...Spin the tires while moving on ice with a limited slip differential and the ass end comes around...
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The correct answer of course is Cheapskates :laugh:
Dusty
<rimshot> :smiley:
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<rimshot> :smiley:
We Need This
(http://thumb.ibb.co/fPzhrF/rimshot_1_gif_c200.gif) (http://ibb.co/fPzhrF)
Paul B :boozing:
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As a northeast kid growing up playing hockey from a wee age outside I can confirm that it's very difficult to skate when it's way cold out-like well below zero. Feels like the skates are in mud.
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As a northeast kid growing up playing hockey from a wee age outside I can confirm that it's very difficult to skate when it's way cold out-like well below zero. Feels like the skates are in mud.
Great evidence there! So you've got temp as a likely variable. To get at whether pressure is another variable, go for a skate when it's cold enough for the skates to feel like mud (-5F or whatever). Then when the skates feel like mud, strap on a backpack loaded with 50 lbs of books, bricks, whatever. Then see if it doesn't feel like mud. Is the physics right with this little experiment? The idea is to have the same 'contact patch' but apply more pressure through it, see if that can form the lubricating liquid layer on top of the ice. Better yet, have a team of JV hockey players do it and have it be their science project. That way you'll get multiple data points.
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As a northeast kid growing up playing hockey from a wee age outside I can confirm that it's very difficult to skate when it's way cold out-like well below zero. Feels like the skates are in mud.
You could be right, but I grew up in a remote mining town on a small island in NW Ont. When we were kids we spent a lot of time skating on the lake (the only indoor ice was the curling rink, and skating there was frowned upon). I don't remember "mud', even at -20.
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Life on earth exists in part because water is more dense than ice. It is one of the four unique things about our planet. The others? We have an extremely large and relatively close moon, leading to substantial tides; we have an atmosphere that is neither too thin nor too dense; and we have a world that constantly rotates at just the right speed.
The combination of cold water sinking (but frozen water rising) and substantial tides means our oceans and larger bodies of fresh water are constantly turning over. This brings nutrients to the surface instead of allowing them to lay on the bottom with no oxygen or sunlight to break them down into useful components. Even further, the movement of the water gets accelerated by the rotation of the earth, creating huge currents. Finally, add in the floating ice at the poles (which conveniently reflects a substantial amount of light) and we have an extension of the warm and cold currents in the ocean into the thinner 'ocean' of air, carrying currents of heat, cold and moisture across the continents.
Eventually, this all leads to the ideal conditions for the rise of life, and the eventual and inevitable creation of Moto Guzzis and roads on which to ride them (Moto Guzzi content!).
Brilliant history of the earth. A good contextual opening. Skip a few billions years of irrelevant bits - and get straight to the point at the end. Moto Guzzi - the pinnacle of evolved life on earth.
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I'm in Buffalo. Snowmobiled up your way plenty of times. We don't get near as cold as you do but we have had that deep sub zero (F) a few times.
I remember some outdoor rinks in Halliburton WAY back when where it was unreal cold. Games seemed in slow motion but that was a few (dozen) years ago!
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" but there's a lot of pressure under a skate blade, like thousands of PSI"
Only if an elephant is wearing them.
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From the google box:
According to the frequently cited — if incorrect — explanation of why ice is slippery under an ice skate, the pressure exerted along the blade lowers the melting temperature of the top layer of ice, the ice melts and the blade glides on a thin layer of water that refreezes to ice as soon as the blade passes.
"People will still say that when you ask them," Dr. Rosenberg said. "Textbooks are full of it."
But the explanation fails, he said, because the pressure-melting effect is small. A 150-pound person standing on ice wearing a pair of ice skates exerts a pressure of only 50 pounds per square inch on the ice. (A typical blade edge, which is not razor sharp, is about one-eighth of an inch wide and about 12 inches long, yielding a surface area of 1.5 square inches each or 3 square inches for two blades.) That amount of pressure lowers the melting temperature only a small amount, from 32 degrees to 31.97 degrees. Yet ice skaters can easily slip and fall at temperatures much colder.
The pressure-melting explanation also fails to explain why someone wearing flat-bottom shoes, with a much greater surface area that exerts even less pressure on the ice, can also slip on ice.
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A 150-pound person standing on ice wearing a pair of ice skates exerts a pressure of only 50 pounds per square inch on the ice. (A typical blade edge, which is not razor sharp, is about one-eighth of an inch wide and about 12 inches long, yielding a surface area of 1.5 square inches each or 3 square inches for two blades.)
That's written by someone who doesn't skate. Ice skate blades are not straight. They have quite a bit of rocker, so the length of contact along the blade is quite short. They're also ground with a concave cross section so they contact the ice at the edges first. Racing skates are often not ground concave, but are very thin compared to figure and hockey skates.
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That's written by someone who doesn't skate. Ice skate blades are not straight. They have quite a bit of rocker, so the length of contact along the blade is quite short. They're also ground with a concave cross section so they contact the ice at the edges first. Racing skates are often not ground concave, but are very thin compared to figure and hockey skates.
Oh, I agree
comma but
The pressure-melting explanation also fails to explain why someone wearing flat-bottom shoes, with a much greater surface area that exerts even less pressure on the ice, can also slip on ice.
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Look at this: https://en.wikipedia.org/wiki/Pressure_melting_point
The effect of pressure on the melting point is negligible until about 50 mPA or 7,250 psi. Even on one skate (12" long X 1/8" wide), the skater would have to weigh 4800 lbs. So it ain't the pressure.
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but wait... ANY pressure must produce SOME heat.... getting confused here....
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OK Prescott , you opened this bag of worms , where are you now ? :laugh:
We may have more than one factor involved here . The worst spill I ever took was on glaze ice , wearing lug sole work boots . Doubt if 160 lbs and relatively soft soled boots caused any heat , as it happened as soon as I stepped onto the ice . Whammo , ouch , damn , what just happened :shocked: :huh:
Dusty
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I'm in Buffalo. Snowmobiled up your way plenty of times. We don't get near as cold as you do but we have had that deep sub zero (F) a few times.
I remember some outdoor rinks in Halliburton WAY back when where it was unreal cold. Games seemed in slow motion but that was a few (dozen) years ago!
Dunno if you were replying to my post, but Haliburton is positively tropical compared to where I was :grin:
(http://thumb.ibb.co/cp9wka/ON.jpg) (http://ibb.co/cp9wka)
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Look at this: https://en.wikipedia.org/wiki/Pressure_melting_point
The effect of pressure on the melting point is negligible until about 50 mPA or 7,250 psi. Even on one skate (12" long X 1/8" wide), the skater would have to weigh 4800 lbs. So it ain't the pressure.
I think you missed my post above.
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I think you missed my post above.
I think you missed my post above.. :smiley:
The pressure-melting explanation also fails to explain why someone wearing flat-bottom shoes, with a much greater surface area that exerts even less pressure on the ice, can also slip on ice.
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OK Prescott , you opened this bag of worms , where are you now ? :laugh:
We may have more than one factor involved here . The worst spill I ever took was on glaze ice , wearing lug sole work boots . Doubt if 160 lbs and relatively soft soled boots caused any heat , as it happened as soon as I stepped onto the ice . Whammo , ouch , damn , what just happened :shocked: :huh:
Dusty
That does pose a question Dusty. I agree, Ice seems to be slippery anyway when you walk (or drive) on it, though to be fair, not nearly as slippery as when wearing a set of ice skates. Could it be that ice tends through it's nature to have quite a bit of free water about? It can't just be smoothness or the same would apply to glass.
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That does pose a question Dusty. I agree, Ice seems to be slippery anyway when you walk (or drive) on it, though to be fair, not nearly as slippery as when wearing a set of ice skates. Could it be that ice tends through it's nature to have quite a bit of free water about? It can't just be smoothness or the same would apply to glass.
John , in my case it was 5 degrees F , and had been well below freezing for several days .
Dusty
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That does pose a question Dusty. I agree, Ice seems to be slippery anyway when you walk (or drive) on it, though to be fair, not nearly as slippery as when wearing a set of ice skates. Could it be that ice tends through it's nature to have quite a bit of free water about? It can't just be smoothness or the same would apply to glass.
Ice is a slippery subject. :smiley: I've read stories of "free electrons" on the surface as well as different classifications of ice according to temperature and pressure.
In cases like this, I tend to see and observe. "Oh, fell on my ass. That must be slick for whatever reason.." :grin:
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While on the subject of frozen water I thought I would share this cool trick. My sister once told me to try throwing a bucket of warm water into the air outside when the temp is 15 below 0 f or less. Well I did and it about scared the crap out of me when it made a loud bang as it flash froze and then hit the ground like shattered plate glass. Didn't expect such a violent episode. Try it sometime, it's amazing to see and hear.
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I think you missed my post above.. :smiley:
I didn't miss it, Chuck. My assumption is that one or two things may be happening with shoes on ice. First, the ice surface isn't perfect, so there may be high pressures in very small areas, and second, the friction theory mentioned above may be more relevant with shoes. But shoes don't glide anywhere near as well as skate blades, so I don't really see a conflict.
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Now that I think about it, ice is always wet. It must be that.
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" but there's a lot of pressure under a skate blade, like thousands of PSI"
Only if an elephant is wearing them.
Actually the above statement is true. The bottom of an ice skate blade has a concave "hollow", so, only the edges actually touch the ice.
(http://newtohockey.com/wp-content/uploads/2015/10/exagerated-skate-sharpening-hollows.jpg)
These edges also give a nice strong lateral grip on the ice, which is what makes tight turns possible.
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Great , now I keep seeing visions of Apollo OH NO :rolleyes: Maybe he knows the answer :shocked:
Dusty
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Now that I think about it, ice is always wet. It must be that.
That could be, and here's a couple of possibilities: Not too sure about this one, but humidity in the air could condense on the ice, then freeze, but there would always be a film of liquid in transition. Then there's the boundary layer problem, where the outermost layer of molecules don't have enough partners to crystalize, so those molecules are "free".
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Free the molecules !
Dusty
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-29C was plenty cold enough for me.
And, we've had the sleds 100 miles North of Timmons. It's lovely up there-but WOW was it cold.
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All materials that rub together produce/have a measurable coefficient of friction.
I suspect that as far as ice is concerned the denser the material contacting ice has a profound effect on this coefficient and coupled with shape and contact of skates on ice gives a relatively low number compared to other materials or shapes. (and probably changes with temps +/-)
A molecular thing?
We in winter aviation ops deal with this coefficient regularly.
So why slippery? cause like so many other things in this world... it is!
:-)
Am ice, therefore am slippery!
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That whispy 98 pound skate queen is still only 98 pounds of downforce on whatever surface area the blade has. Add some velocity and things change. Angular momentum any one? All we need now is some cabin fever riddled Guzzi folks to spoon on some studded ice tires and tow the volunteer skater across the lake. Do some turns while filming the event and have a temp sensor on the blade. It's winter(not here), we need some entertainment.
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-29C was plenty cold enough for me.
And, we've had the sleds 100 miles North of Timmons. It's lovely up there-but WOW was it cold.
Oh yeah. My elderly cousin lives in Timmins and she's always envious of me being in southern Ontario now. I'm not far from you in Kitchener-Waterloo. Right now it's about -6 here, -23 in Timmins, and -29 in Red Lake where I was born and raised.
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Seems like a simple question, right?
Another perhaps related question..why does ice adhere to all solid non-heated objects?
Best Regards,
Peter
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'cause ice molecules like to stick to everything especially wings and windshields!
:-)
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From the google box:
According to the frequently cited — if incorrect — explanation of why ice is slippery under an ice skate, the pressure exerted along the blade lowers the melting temperature of the top layer of ice, the ice melts and the blade glides on a thin layer of water that refreezes to ice as soon as the blade passes.
"People will still say that when you ask them," Dr. Rosenberg said. "Textbooks are full of it."
But the explanation fails, he said, because the pressure-melting effect is small. A 150-pound person standing on ice wearing a pair of ice skates exerts a pressure of only 50 pounds per square inch on the ice. (A typical blade edge, which is not razor sharp, is about one-eighth of an inch wide and about 12 inches long, yielding a surface area of 1.5 square inches each or 3 square inches for two blades.) That amount of pressure lowers the melting temperature only a small amount, from 32 degrees to 31.97 degrees. Yet ice skaters can easily slip and fall at temperatures much colder.
The pressure-melting explanation also fails to explain why someone wearing flat-bottom shoes, with a much greater surface area that exerts even less pressure on the ice, can also slip on ice.
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That's written by someone who doesn't skate. Ice skate blades are not straight. They have quite a bit of rocker, so the length of contact along the blade is quite short. They're also ground with a concave cross section so they contact the ice at the edges first. Racing skates are often not ground concave, but are very thin compared to figure and hockey skates.
1 time the wife & I went onto a steel grated bridge over a river on our CX100 bent over because the road was not straight approaching the bridge, it was kinked, and we had never been on this road before. We leaned right, the bike immediately laid over on it's right side, and the bike & us slid across the bridge as if it was ice! The wet grated steel was so slippery we could hardly walk on it and we didn't get hurt because we just slid `till we stopped! The bike didn't fair as well as we did since the right jug/head hit the steel and the fin fender broke off, the spark plug broke in half, the head fins broke off too, all of which immediately fell into the river below! :shocked: And yet the bike was still running on the left cylinder while laying on it's right side. 2 kids saw our whole ordeal and 1 of them said, "hey mister, you bike is still running." So I carefully walked over to it and turned the key off. The front brake lever was toast too. So if you approach a wet steel grated bridge, make sure you approach it in a straight line and be carefull. :evil:
Come to find out many bicycle riders get hurt on that old bridge too.
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Wait , why does your tongue stick to an ice cube ? Something ain't right with all this theorising :shocked:
Dusty
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Wait , why does your tongue stick to an ice cube ? Something ain't right with all this theorising :shocked:
Dusty
That's not true. If you want your tongue to stick to something cold, it can't be an ice cube because the IC will start to melt from the heat of your tongue. Your tongue sticks to metal that's cold enough, which doesn't melt. :evil:
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It's the whisky you pour over it that makes it slippery. Duh
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If you let ice sneak up on you, it can kill you!
(http://i1299.photobucket.com/albums/ag77/Penderic/Penderic004/icicles-on-roof_zpstrik6xaf.jpg)
Dangerous!
(http://i1299.photobucket.com/albums/ag77/Penderic/Penderic004/car-skidding_zpsxjyeyylz.jpg)
White knuckles!
(http://i1299.photobucket.com/albums/ag77/Penderic/Penderic004/700_zpsm8q4xkwi.jpg)
Where'd she go?
(http://i1299.photobucket.com/albums/ag77/Penderic/Penderic004/69593081.WJRVitYB.rimshot_zpsg5y62wlc.gif)
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We used to go through this as an exercise in engineering classes. Along with the idea that hot water freezes faster than warm water when put in a freezer.
The logic goes back to molecular physics. The surface molecules are not bound as tightly to the 'ice' as the inner molecules. There is always some vaporization going on depending on external conditions. So, there is a layer of 'loosely bound' molecules on the surface (water is not a good description). That would not be enough by itself to make ice slippery. You also need it to have a 'smooth' surface. That comes from the underlying material, or, a built up layer of ice. So, a smooth surface and the resulting low friction makes it slippery.
Another 'experiment' is to put something on the ice and let it sit. After a while it will be frozen to the ice (including ice skates). That layer of 'loose' molecules now are 'internal' and will 'freeze'.