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When braking on ice skates I often wonder how the "shaved" ice particles spray away with high velocities on both sides of the blades. Especially when the ice skate is already slow the flakes still fly at high speed against the direction of motion. What is the mechanism of their paradox acceleration?

To see what I mean, look at

https://www.youtube.com/watch?v=sf-cINNfRQo

e.g. at 0:28 or 0:52.

I

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It's the same idea as when a rifle is fired. The rifle moves backwards relatively slowly, but the lightweight bullets move forward at high speed. It's conservation of momentum, substitute ice particles for bullet and skate boot and blade for the rifle. It might look as though the ice particles are continually accelerating, but they only accelerate at the lift off point at the surface of the ice.

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As the skate passes over the ice, it compresses portions of it between the blade and lower layers of ice. Some shavings may be accelerated by being squeezed out.

Just like a small movement of your fingertips can squeeze a watermelon seed to high speed, a small movement of the skate can squeeze some of the shavings up into the air.

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  • $\begingroup$ Makes more sense than my answer, unfortunately the video is not very HQ but I can't see any spray on fast movement, but when it focuses on the slow part, then the spray of ice is obvious. $\endgroup$ – user140606 Feb 9 '17 at 0:00
  • $\begingroup$ I imagined a similar mechanism but felt somehow dissatisfied. Partly because it's impossible to verify the assumed shearing of the ice. Further you can't easily remodel the situation by any physics simulation engine or find a comparable experimental setup which displays similar behavior. It would feel good to read an analytical estimation based on typical parameter values. $\endgroup$ – Alexander Fischer Feb 9 '17 at 20:41

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