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?"

Why use a rotating disk?

[SonicBurst]

Why not just use some treadmill like contraption? Seems like you'd circumvent all the centripetal force/motion problems that way.

what if the "record" gets a "scratch" ;)

[Xzzy]

When this thing is running at full tilt, how the hell do you get off it? Or worse yet, where do you go if you fall, as is sure to happen.

Seems to me there's a lot of issues with physics involved as well, ignoring the problems of getting the thing to actually operate.

People learn to ski on solid, non moving surfaces. What happens when you try to stop.. do you overbalance and fall down? Or how about the race track problem.. you're always turning left, cuz if you turn right you run into the wall.

Basically I see this thing creating more questions than solutions. :p Be nice if the article was more than a brief overview.

How do I get on?

[boio]

So how do I get onto this thing? It seems like it would be hard to get started on it since it's constantly moving - and even harder to get off of it.
It would also get pretty boring to ski around in a circle for hours on end... no new scenery. If they put up a big contiguous screen along the edges, and maybe some of the sky too, to prevent you from getting quite so dizzy and provide some additional entertainment.
Then again you could also just go VR skiing and never have to go outside or worry about all these physical limitations.

Re:Why use a rotating disk?

[jacoberrol]

well, actually, a skier's top speed is mostly determined by the slope of the run, weight of the skiier, type of skis etc. your maximum speed relative to the track would be no different on the inside or outside. of course, if you ski too fast on the inside then you get to the bottom. ski too slow on the outside and you would rise to top.

uhh..not me

[crystalplague]

"However, Nenad Bicanic of the University of Glasgow says that the structure may be feasible. But he says precautions would be needed to ensure skiers could not be pulled into the mechanism at the top of the slope."

I think I'll let them work the bugs out first.

That will not work

[Edmund Blackadder]

I suppose he wont be skiing straight down so he will need to make turns. Yet when he is making turns, if he is on one side of the slope it will be moving faster under him then if he is on the other side. I have a feeling this discrepency will quickly cause him to fall.

Chairlifts...

[Chazmati]

No chairlifts sounds nice. If you out-ski the turntable you just pull off to the side and ride to the top, then hit the trail again.

But chairlifts also meter traffic. I'm talking out my butt here, but I'm sure that ski slopes do some kind of calculations involving skiers/hour and trail capacity. Without a traffic limiter, the turntable could get 'too busy' on heavy days.

Re:The perpetual slope already exists

[ackthpt]

They have one here in the Calif. central coast area I live in, at a snow board shop. Ok if you want to keep in practice or get ready for the real thing, but no substitute for it. You just stand in place and move from side to side.

What this guy has in mind is like an upended record, on a much larger scale, more terrain to move about in, but ultimately still what I would consider a dull experience. Probably good for teaching beginners and little else, since the inside and outside of the track would be moving at different rates you'd get pretty good at turning one way, but would find difficulty adjusting to a real slope. Nothing like screwing up your motor skills and equilibrium.

IMHO it looks terrible. I'm sure it'll be a hit.

So have it slope up towards the middle?

[GlenRaphael]

[due to the "skating force"] Skiers would be drawn toward the middle of the disk and would have to be constantly turning outward to avoid hitting the spindle at the center of the terrain.

I'm not sure I get the physics involved in this assertion, but it seems like it you could discourage people hitting the spindle by building up the middle of the disk such that you have to ski "uphill" to get to it.

Re:Subject to the ``Skating Force'' of LP days

[Anonymous Coward]

I have to diagree. The reason the tea-leaves pile up in the center is that despite being waterlogged, they still have lower specific gravity than water. They are less dense, they take up more volume than the water they displace. Ordinarilly, this would cause them to float, however, since they are wet, the added mass of water drags them down. The piling you observe is a result of the fact that the water is pushing outward (centrifugal force) and is denser than the leaves.

There is a lot of debate over the differernce between (or the lack of difference between) centrifugal force and centripital force. They are opposing forces that are caused by the same basic relationship of the motions of two objects, but from the different points of view of the objects concerned.

The force of the cup (inward) opposes the outward force, (the tendancy of the liquid to want to continue in a straight line, the centripital (towards the center). The force it opposes, the liquids tendancy to try to go outward due to spinning, is centrifugal. Bear in mind this is the result of a lack of momentum in a direction, and moment in one direction changing into moment in another.

(Note that, per Newton, a book on a table experiences the force of gravity towards earth. It exerts downward force on the table, which though very passive, exerts AN EQUAL AND OPPOSITE force upwards on the book. And you thought it just sat there, huh!!! If the table did not exert this force, the book would bend the table or rip through it. Think of a little tiny kiddie table with a book, and an elephant standing on the book. The table cannot equal the force being placed upon it, and yields.)

To put it another way, the gravity of earth exerts a centripital force on the moon, as the moon orbits, (or "falls around") the earth, and the moon's linear velocity counters that force, by exerting a centrifugal force on the moon, (pushing it outward).

Like I said, the two opposing forces which act on a single object, in this case, to keep it in one place (in orbit, for example) rather than flying off.

If you don't believe me, try this: Take a helium balloon with a bolt or washer or something tied to it's string, and put it on the passenger seat of your car. Then accelerate forward. You'd probably expect the balloon to move backwards, relative to the car, trying to stay in one place (lack of momentum in a direction, usually and more simplistically called inertia) but the balloon moves forward, at least until the bolt stops it. This is because the air is more dense, pushing the balloon forward while it (the air) moves back.

Of course, I could be wrong.

P.S. Old != smart, old != right. Not of neccessity, anyway. And there are plenty of people on slashdot who probably owned a dinosaur as a pet at some point. :-)