Some Canadians watch curling almost as intensely as hockey. During a game, there is often much discussion about which shot to throw, how hard the rock should be thrown, and when the rock should be swept. Why is there so much discussion? It all comes down to physics.

Did you know? The water-repelling granite used to make curling stones is only found on the island of Alisa Craig, off the coast of Scotland, and at a second quarry in Wales.

One of the most important elements of curling is the ice. Curling ice differs from skating ice in that it is pebbled, meaning that the ice is sprayed with water to create a textured surface. This pebbling reduces the amount of surface area in contact with the curling rock. Also, if you were to turn over a curling rock, you would see that only a narrow ring (called the running band) is actually in contact with the ice. The result is less contact between the rock and the ice, which lowers the amount of friction and allows the rock to travel further down the ice.

Friction also relates to one theory of how the sport got its name. Given a gentle turn, the rock will “curl” to the left (counterclockwise) or the right (clockwise) as it travels down the ice. Many different factors cause the rock to curl. For example, as it travels down the ice, the front of the rock exerts pressure on the ice and a thin liquid film is created. This film causes there to be less friction at the front of the rock than at the back.

Did you know? A typical curling stone has a diameter of 250 mm, while its running band measures about 120 mm in diameter with a width of 5 to 7 mm.

If you were to follow one spot on the outer edge of the rock as it rotates, you would see how it encounters more friction as it leaves the slippery front section and moves toward the back. According to one proposed model, this causes some of the forward momentum to transfer into a sideways motion, and results in the stone curling in the direction of rotation (see Science World Blog).

These are only a few examples of how some researchers understand the relationship between curling and physics. The laws of physics can also help explain exciting shots such as the double takeout and the hit and roll. So next time you are in the hack and wondering what to do, look to physics for the answer!

Learn More

Science World Blog (good summary of why curling stones curl)

What puts the curl in a curling stone? Reprinted from Canadian Curling News, March 2000 issue.

Curling is fine example of physics at work in real world. Science Alberta Foundation

How curling stones are made (Video)

Image by Benson Kua via Flickr Creative Commons

Article first published February 15, 2012

Candace Piper

I am a Masters student at the University of Saskatchewan. For my research, I am studying how an invasive species interacts with other plants in the community, the microbes that live in the soil, and how this might affect soil nitrogen cycling. I grew up in Saskatchewan, and so grassland ecosystems are close to my heart. In my spare time (if there is any), I like to knit, do crafts, and play sports, such as volleyball and ultimate frisbee. 

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