If you’ve been keeping up on your Physics 111 blog post readings, you’d know that Emily Schweitzer is the fearless leader of Colgate’s Curling team. I, although not nearly as skilled, am also a curler, and am fascinated by the physics that makes curling work (like nearly perfect elastic collisions, angular motion, etc.). If you need a basic introduction to the sport as a whole, as it’s important for my post, here’s a wonderful crash course: https://www.youtube.com/watch?v=IOk9SVzqHsk
There has recently been significant strife in the curling community about certain synthetic fabrics that have been used to make the broom heads for sweeping. These new broom heads have different properties such as less waterproofing, artificial textures/hairs, and different kinds of padding, all which have the ability to melt and carve into the pebbles on the ice much more effectively than the standard broom heads. The concern here is that this new technology allows for cheating and lessening the skill required to curl well, as rocks can be manipulated much more when the brooms are much more effective at changing the ice in its path.
The main logic as to why the sweeping helps the stone travel farther is that by momentarily raising the temperature of the ice, but not melting it, you reduce the kinetic coefficient of friction, slowing the stone down less. You do not want to melt the pebbles on the ice, because then you are increasing the amount of surface area the stone has in contact with the ice, increasing the frictional force on the stone.
I wanted to more thoroughly understand why these different types of broom heads change the ice in different ways. The standard broom head is padded and made of nylon coated in a waterproof material, and in this example I will examine what would happen if you swapped the fabric out for something that creates more friction with less padding, as done in the newly popular icePad broom head (which is banned in some levels of competition). This is supposed to increase the overall power of the sweep by reducing the surface area wasted on the unpebbled ice, allowing all of the frictional force to be concentrated on the pebbles. This change in fabric is also shown to create more friction between the broom and the ice to heat up the ice more, causing less friction between the stone and the ice. These two manipulations allows a sweeper to exert far less energy to manipulate the stone much more effectively.
If you're looking to read more on this, here’s a few articles that discuss this issue more in depth:
As for now, the verdict on new broom technology is as follows: use a standard broom, and there’ll be good curling!