About Science?

Question

Why does an ice skater move across the ice faster than a runner on an asphalt track?

Answer 1

Actually, the lack of friction is only a relatively small part of the explanation. Lower friction only means that the skater doesn't lose much forward speed between sweeps of the blades, and that the blades move very efficiently. But if that were the only difference, then the skater could still never move any faster than their foot speed - just like a runner.

The big difference is all about the mechanical advantage of an inclined plane.

The blades on the skates are inclined planes, which translate sideways push into forward motion. The steeper the angle of the blades (more parallel to the forward motion) the greater the mechanical advantage. The shallower the angle (more perpendicular to the forward motion) the less the advantage.

If the blades are pushed at a 45-degree angle, 1 foot of sideways push equals 1 foot of forward motion. If pushed at about a 26.5-degree angle, 1 foot sideways equals 2 feet forward. A 14-degree angle gives 4 feet forward for every 1 foot sideways. And so on.

A speed skater will hardly have any angle at all (very steep) and will therefore reach very high speeds. Lack of friction just makes all this easier.

Answer 2

Basically, the difference is entirely due to friction. Both a runner and a skater move at about the same speed when they start off, but the skater can continue adding to his or her forward momentum with each step because hardly any of it is lost due to friction. The runner, whose shoes aren't likely to slip on the asphalt, can only replenish his or her original forward momentum with each step.

If you want to get down to the physics of the skater's blades, the thin edge of the blades sliding across the ice heat the ice enough for it to melt. Essentially, the blades are only sliding across a very thin lubricating layer of water.

Answer 3

There is less friction on the ice. There is a higher force of resistance against the runner on the track than there is against the skater, thus allowing the skater to move faster with less resistance.

Answer 4

Less friction.