Why do skis slide on snow?

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Offline Geezer

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Why do skis slide on snow?
« on: 28/11/2010 18:54:06 »
I believe there was a lengthy thread on the subject of how ice skates work, but I'm not sure if skis operate for the same, or somewhat different reasons. Certainly, the pressure exerted between the surface of a ski and snow is a lot less than the pressure exerted by an ice skate on ice.

Also, skis are usually waxed, and the characteristics of the wax can make quite a difference, depending on temperature.

Any clues?

UPDATE: BTW, this came to mind because of the amount of snow we've had here. So far, it's about sixteen inches, and it's not even December yet. Last year, we didn't even get sixteen inches during the entire winter!
« Last Edit: 28/11/2010 19:03:05 by Geezer »
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Offline maffsolo

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Why do skis slide on snow?
« Reply #1 on: 28/11/2010 20:27:48 »
Skiing over snow is a combination of both wet friction and dry friction: too much water will create "wet drag" (suction), while too little water will result in "dry drag" (friction). A properly selected glide wax will aid in this delicate balance.

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Offline Geezer

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Why do skis slide on snow?
« Reply #2 on: 30/11/2010 07:20:03 »
In one of the Richard Feynman interviews on Youtube, he seems to suggest that the effect on ice might be related to the fact that water expands when it freezes. Was he speculating, or was he on to something?
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline jartza

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Why do skis slide on snow?
« Reply #3 on: 30/11/2010 07:37:23 »
Feynman means melting & compression is related to freezing & expansion

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Offline Geezer

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Why do skis slide on snow?
« Reply #4 on: 30/11/2010 07:45:29 »
Feynman means melting & compression is related to freezing & expansion

Quite possibly. How does that effect the phenomenon?
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline jartza

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Why do skis slide on snow?
« Reply #5 on: 30/11/2010 08:00:35 »
When you force ice to water's density the ice turns into water.

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Offline Geezer

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Why do skis slide on snow?
« Reply #6 on: 30/11/2010 08:38:45 »
When you force ice to water's density the ice turns into water.


Is that what skis do? I don't think they exert a great pressure.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline jartza

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Why do skis slide on snow?
« Reply #7 on: 30/11/2010 09:08:12 »

I'm not knowledgeable about skis. I just had to tell what R Feynman was thinking.