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The physics of ice skating. A lesson focusing on friction.

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If you have ever traveled across an icy sidewalk you know that there is definitely an issue with traction and ice.  I’m visualizing scenes from movies (and my real life) where people (me) were sent sprawling across an icy expanse only to be tortured by the act of trying to get back upright again.

Taking advantage of this reduced friction is a favorite winter past time. Our favorite winter activity is sledding (on the rare occasions when it snows).  There are lots of winter sports and activities that use the snow and ice to their advantage.  There is an entire set of Olympics dedicated to winter sports.

 

 Laws of Motion

What about ice skating?

How do skaters do it?  Some of them do it beautifully and others are able to command speed and stick handling that all wind up leaving you a little in awe.

 

Full disclosure: I’m from the southeast where our exposure to ice skating is limited at best.  I’ve been on ice skates only a few times.  My kids even less. We were invited to go out to a homeschool ice skate this week and I wanted to be a little more prepared.  For me, that usually includes science.

 

The physics of ice skating.

 physics of ice skating
We know ice is slippery.  There are lots of theories as to why that is the case.  One of the prevailing theories currently, is that there is always an extremely thin layer of water on top of the ice that lubricates the ice and reduces friction causing those slippery falls.

 

In order to prevent falls, there has to be enough friction to create traction to prevent falling AND allow the skater to move forward.  Those two things are accomplished by the sharp blades on ice skates.  The blades dig into the ice that allows the skater to stand and push off with their leg muscles to create the force necessary to move forward.

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Movement and Forces

In case its been a while since your last physics lesson, a movement is the result of unbalanced forces.   In the case of ice skating, friction has to be overcome in order to have movement.  The leg muscles will need to push against the blade to propel the skater.  The blade will have enough friction to stick to the ice because the blade literally digs into the ice.

 

This is assisted by a skating stance that usually has the mass balanced slightly forward.  The skater will continue to move because the friction force is very low and the skater will need to create more friction (by turning the skate) or hit a wall in order to stop.  Newtons’ First Law of Motion.

Field Trip

Armed with our new knowledge we were determined to go on an adventure and stay upright (at least some of the time)
The key ingredients:
  • crouching down
  • pushing off from one leg (at a slight angle) while gliding the other skate.
  • to stop turn the skate to increase the friction (or hit a wall)

physics of ice skating

 

Don’t have an ice skating trip planned?

You can still explore friction with the kids.  If you are like me, you might envision the world’s worst case of carpet burn when you combine the words friction and kids.  There are lots of other options.




A great experiment is a cutting board (we used plastic) and a variety of objects like a rubber eraser, ice cube, plastic toy and paper clip.   Hold up the cutting board and see which one moves first? Which one moves fastest?  You are demonstrating two different types of friction.

Friction Forces

 

Dynamic and static friction

Dynamic friction occurs between two objects that are moving relative to each other.  That means they rub against each other.  That is what happens when you a sled rubs against the ground or when your kid drags your other kid across the carpet and someone gets carpet burn.

Static friction occurs between two objects that are not moving relative to each other.  This is the type of friction that keeps an object from moving (like not sliding down a hill or when you put snow boots on with better grip to increase the friction and help you stand up in the snow).

In our experiment, we see static friction as we have to increase the angle of the cutting board higher and higher to cause the objects to move. Eventually, the pull of gravity is greater that the force of friction and the objects move.  We see dynamic friction at work (or not ) when the objects fly across the board.

physics of ice skating

When the ice melts we begin to see it moving across the board faster and faster.  This is a result of the lubricating nature of water decreasing the friction between the two solid objects.  This is the same thing that oil does in an engine.

We assisted this process with a spray bottle of water.  Have fun with friction, but try to keep the carpet burns to a medium.

 

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This is the first in our series on the science of winter sports.

Laws of Motion

 

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