Slashdot Mirror
Perpetual Skislope
the hollow room writes: "How about skiing on a never ending slope? A story at New Scientist suggests that some fool is going to try to build one of these. Built like a huge tilted record player, it can spin at up to 30 km/h.
Any takers?"
One advantage of a disk is that you get different speeds a different points on the radius. if you want to ski faster, you just move out instead of moving to a different treadmill.
Movies of a working ski-trak!
Okay, it's just a model but they answer the everyone's question about getting on and getting off - there's a stationary area in the middle
The japanese have been skiing indoors for years. You can have climate controlled fun year round here at the Tokyo Skidome:
Indoor Skiing
Your guess is wrong - it's the drag skiiers are trying to reduce when they tuck. These guys are going over 60 mph - wind resistence is a big deal.
XML causes global warming.
It just doesn't work that way. A disc and a sphere of the same weight will simply not roll downhill at the same speed, even in a vacuum. Besides, the very act of lowering one's center of gravity 1.5 feet would have a definite impact on momentum.
You are comparing different issues. The skiier is not rolling. If the skiier were trying to roll down the hill, then you would be correct, but the momentum that you're describing is rotational momentum, not translational. With translational momentum, it doesn't matter. A proper comparison would be to push an object across a table (like say your CPU and your monitor); they have very different geometries, but the only forces acting on them are your push and the friction of the table (until you get to high speeds when wind resistance matters).
"You know how figure skaters pull their arms into their bodies to increase their rotational momentum?"
It is not the same. Unless you spin like a figure skater when you ski down the hill.
"The physics of a tight, compact body with a low center of gravity..."
The low center of gravity helps when you are trying to turn (change direction), but the biggest advantages to tucking deal with lowering wind resistance and tensing your muscles like springs to react faster.
You're right that disc and a sphere will not roll downhill at the same speed. That's because the moment of inertia changes. However, a skier does not roll -- he slides downhill.
Just write down the equations for potential and kinetic energy and you'll see that changing the center of gravity won't change shit as far as the speed goes.
Moving the center of gravity up or down changes the potential energy, but since its reference level can be chosen arbitrarily it will have no effect in how much potential energy can be converted to kinetic energy.
The owls are not what they seem