Physics question

indianroads

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Suppose you are in space within a very large rotating cylinder that will simulate gravity.

Within that cylinder someone has constructed a tall building, say 6 stories tall (it's a big cylinder). As you climbed up through the stories, would gravity increase, decrease, or remain the same?

ETA:
As you went up, the rotation speed under your feet would increase, so would the Coriolis affect might be more pronounced?
 
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MaeZe

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indianroads

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Sage

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If a guy is standing on the first floor of your 6-floor building and a girl is standing on the top floor, the rotational speed would be the same, but the distance the guy would travel would be greater than the distance the girl would travel in the same amount of time. I believe this lessens the centripetal force on her (which is what gravity would be in this case), so the gravity would be decreased. At the center there is no centripetal force.

However, I believe that the bigger the cylinder is, the less effect the building would have on gravity. A 60-ft building in a cylinder with a 100-ft radius would have a greater change in gravity than that of a 60-ft building in a cylinder with a 100-mile radius.
 

MaeZe

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...the rotational speed would be the same, but the distance the guy would travel would be greater than the distance the girl would travel in the same amount of time....
That confuses me. If I travel further in the same amount of time, I had to have gone faster.

However, the whole thing confuses me so when that happens ... :popcorn:
 

Albedo

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Rotational velocity is distinct from true velocity. The two people have the same angular velocity about the axis (measured in angular change over time), but the person farther from it has greater true velocity.
 

Albedo

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To OP's original question, depending on the diameter of the rotating bit, the coriolis forces do increase as you ascend, and in a small enough habitat might be debilitating at higher levels. Good luck trying to walk around without hilarious projectile vomiting when your head is feeling different coriolis and gravity to your feet. It's my understanding that the coriolis is worse close to the axis because the ratio of angular change to distance traveled is greater. The centrifugal force/gravity is of course less for the same reason.
 

MaeZe

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So you could solve the problem by having a funnel shaped skyscraper.

Still leaves me totally confused how it culminates at the axis.



MaeZe, who loves to learn new things.
 
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Beanie5

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A sufficiently small rotating habitat is basically a tumble dryer.

Which means, of course, that when we get the first orbital stations that work on this principle, we will also find out that somehow cats got onboard and oh man, are they ever FREAKED now...
 

MaeZe

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Rotational velocity is distinct from true velocity. The two people have the same angular velocity about the axis (measured in angular change over time), but the person farther from it has greater true velocity.

It took me a day, but by George, I get it!:hooray:
 

indianroads

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In space, nobody can find your missing socks...

I mean, seriously, where the heck are they going? It's a space station! Dang it, never should've let Whirlpool design this thing...

All this talk makes me feel a tiny bit more normal, this problem confused me.

Oh wait... I'm chatting with authors... so scratch the 'normal' remark.
 

phantom000

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Well, as Yoda said to Luke "Unlearn what you have learned." It's one of those things that can be very easy to understand provided you are willing to let go of your 'common sense.'

If you think about a CD or a DVD, as it spins a point on the outer edge would have to travel further then a point on the inner edge, but has to travel it in exactly the same time. Therefore the outer edge must be moving faster then the inner edge. In a spinning cylinder gravity is simulated by the rotation which pushes you down against the inner edge, the faster the rotation the stronger the force. So yes, in what you describe a person on the top floor of your building will experience less gravity then someone on the bottom floor.

That being said, I would like to ask how big this cylinder really is. If its big enough the difference would be so small that you would never feel it.
 

nickj47

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For your typical colony-sized cylinder, say 10 kilometers across and rotating once every 142 seconds, the difference in acceleration ("gravity") between the base and top of a 20-meter high building would be about 0.039 m/s-squared, or about four-tenths of one percent of Earth's gravity. Measurable, not noticeable. Speed of the base of the building would be 221.2 m/s, or about 495 mph. Speed at the top would be 220.4 m/s, or about 493 mph.

Unless I got my math totally wrong.
 

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Think of it this way.

You are standing on a horizontally spinning platform, like a (merry-go-round?) at a children's playground. If you stand near the edge of the circle and i spin it hard enough, you'll go flying off. If you stand directly in the center, you'll stay in place and just spin in circles without feeling any of the "gravity".

So, the higher up you went in the building, the less "gravity" you would feel.