Physics of Curling

One of my favorite sports to watch during the winter Olympics is curling. Curling may seem simple and boring on the surface, but it is really a complex sport with much skill and strategy involved. There are two important principles of physics that influence curling. The first principle is friction. According to Newton's third law of motion, for every action there is an equal and opposite reaction. So, as the stone slides along the ice, it exerts a force on the ice, and the ice exerts a force back on the stone. Friction can be defined as the reaction of the ground to the forces exerted on it in the horizontal plane by the person or object (in curling, we are concerned with the stone). The friction force on the stone will act in the opposite direction in which the stone is moving, and will decrease the stones velocity, thus slowing it down. If the curlers want the stone to travel further, then they need to reduce the amount of friction. This is done by "sweeping" the ice in order to make it smoother and reduce friction. Sweeping is also done to make the stone "curl."

Another important principle of curling is collisions. One of the strategies in curling is to knock the other teams stone(s) out of the house (scoring area). This involves the collision of one or more stones. Collisions occur frequently in sports, such as hitting a baseball, tennis ball, volleyball, etc. Again, because of Newton's third law, when two objects collide, they exert equal and opposite forces on each other. The sum of the momentum of the two objects will be the same before and after the collision, therefore, there is a conservation of linear momentum. Momentum is defined as the mass of an object or system multiplied by its velocity. Most curling stones have a mass of around 20 kg. So, a stone with a mass of 20 kg and velocity of 7 m/s (meters per second) linear momentum (G) would be 140 kgm/s. When the stone that has been delivered collides with a stone in the house, a change in momentum will occur between the two stones. Because the mass of the stones will remain constant, the change in momentum will be related to the change in velocity of the two stones. Because of the conservation of linear momentum, if the stone in the house's velocity increases to 4 m/s (from 0 m/s before the collision because it was stationary) after the collision, than the stone that was delivered will have a decrease in velocity from 7 m/s to 3 m/s. Check out the video below for some good curling throws.

Top Curling throws