Friction is...
- Resistance one thing encounters when moving over another thing (two things rubbing against each other)
- Friction is what keeps things from sliding
- Friction is present whenever objects come in contact with each other
- Friction acts in the opposite direction of the way the object is traveling
Why is gliding on metal blades across solid surfaces smoothly impossible, but possible on ice? Why is ice so slippery?
In order to ice skate, there must be as little friction as possible so that the skaters are able to glide over the ice so smoothly. Ice itself is not what is slippery, but rather the water on the ice. Underneath the blade of figure skates, there is a thin layer of water from the melted ice. When the blades of the skates glide over the ice, there is heat generated causing the ice to melt. The ice molecules loosen up creating an almost frictionless surface. This water then acts as a lubricant (something whose purpose is decreasing friction), resulting in smooth motion over the ice. The water molecules on the ice surface are in between a liquid and solid state, allowing such smooth motion. However, the ice does not just melt completely, it is automatically refrozen and transformed back into the ice it originally was. Take a look at the video below.
The coefficient of friction between ice and the blade is almost zero, so the only way to propel is to push off the ice with a force perpendicular to the skate blade. In order to spin, you must dig your blade in the ice (using the toe pick on the front of the blade), because the level of friction is so low and friction is what enables something to turn (friction is present when you dig your blade in the pure ice). Ice skating would be impossible if it were not for the low level of friction due to the thin layer of water on the ice. Skating on ice itself without water would be equivalent to skating on glass or cement.
Blades are skinny for a reason. If blades had more surface area, that would increase friction and make it harder to glide on ice. Ice (with the layer of water) consists of so little friction already, but with such skinny blades, there is even more decreased friction, allowing you to skate smoother and faster.
The coefficient of friction between ice and the blade is almost zero, so the only way to propel is to push off the ice with a force perpendicular to the skate blade. In order to spin, you must dig your blade in the ice (using the toe pick on the front of the blade), because the level of friction is so low and friction is what enables something to turn (friction is present when you dig your blade in the pure ice). Ice skating would be impossible if it were not for the low level of friction due to the thin layer of water on the ice. Skating on ice itself without water would be equivalent to skating on glass or cement.
Blades are skinny for a reason. If blades had more surface area, that would increase friction and make it harder to glide on ice. Ice (with the layer of water) consists of so little friction already, but with such skinny blades, there is even more decreased friction, allowing you to skate smoother and faster.