artificial gravity

[essentialsaltes]

If you are INSIDE the 'spinning station (described above as a ferris wheel)
your mass is being thrown to the wall of the circumference 'gravity' that is created by 'centrifugal force'

Centrifugal force is what we call a fictitious force. It does not exist. It is just an artifact of a rotating reference frame.

No, the floor doesn't push up, you push against it

Both, really. Newton's Third Law says that "When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body."

If you are pushing against the floor, the floor is pushing against you.

the base of the bucket DOES NOT 'push up', it merely contains the water, preventing it's escape

It can only prevent its escape by exerting a force. Forces cause a change in motion. If the water's motion would be different without the bucket, then the bucket must be exerting a force on it.

 

[whois]

If you are INSIDE the 'spinning station (described above as a ferris wheel)
your mass is being thrown to the wall of the circumference 'gravity' that is created by 'centrifugal force'
that wall contains you, like the base of the bucket contains the water within the bucket

correct, as long as you stay in contact with the station.
as soon as you lose contact with the station, your motion is determined solely by your initial acceleration properties (speed and angle).
you have to remember that there is no gravity on the station, and this is what you seem to be forgetting.
another thing to remember is that the acceleration increases along the radius of the station.
at the axis you could float weightless, but as you approach the rim your "weight" would increase.
this is why all of the effects mentioned above are more pronounced on a short radius station.
i found some material on artificial gravity and will upload them in my next post.

 

[whois]

i found all of these files on my hard drive last night.
i have no idea where they came from, the internet obviously, but can't remember the specific site.
i have more, but they are way too large to upload.

 

[durangodawood]

Neat thread. Where's the creationist angle?

 

[Loudmouth]

No, the floor doesn't push up, you push against it
the base of the bucket DOES NOT 'push up', it merely contains the water, preventing it's escape

As noted by others, the bucket does push back on the water.

You are NOT being accelerated, you are contained within a pressurised ring
one, that is spinning in a vacuum (Space).

An object spinning next to you does not contain you. Unless you are physically touching the ring, why would you move in the direction the ring is spinning?

You are moving at the same speed as the ring (ferris wheel) is spinning

Not if you just move up to it from somewhere else.

 

[Davian]

For those old enough to remember the TV show Babylon 5:

There was an episode where a character looks out of their window of their cabin in the spinning section of the station, to see a spacecraft/fighter/ship "hovering" outside the window.

Q1: do you recall which direction the ship's thrusters were visibly pointed to maintain its position outside the window (for TV-physics)?

Q2: in which direction (in relation to the ship's axis) should they have been pointed (in reality)?

 

[davedajobauk]

Centrifugal force is what we call a fictitious force. It does not exist. It is just an artifact of a rotating reference frame.



Both, really. Newton's Third Law says that "When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body."

If you are pushing against the floor, the floor is pushing against you.



It can only prevent its escape by exerting a force. Forces cause a change in motion. If the water's motion would be different without the bucket, then the bucket must be exerting a force on it.

note: a gallon of water weighs @ ten pounds

If, a length of string with a safe capacity of 12 lbs
is attached to the handle of the bucket containing the water
and the bucket is swung around at increasing speed, the string will break
~indicating, that the weight of the bucket and water
has become heavier (?)

The influence of earth's gravity has been negated, in favour of the
centrifugal force containing the water in the bucket
So, it is, far from being "a negligible / imaginary 'force' "





This thread is becoming full of argument and denial
and little practical thought is being employed
ergo: choices of individual opinion challenge others, without proof
or eminent experience

I am therefore withdrawing from this thread
My having nothing useful or encouraging to add

 

[essentialsaltes]

If, a length of string with a safe capacity of 12 lbs
is attached to the handle of the bucket containing the water
and the bucket is swung around at increasing speed, the string will break
~indicating, that the weight of the bucket and water
has become heavier (?)

The weight of the bucket and water is the same as the force of gravity on them. It does not change if you swing it around.

The 'safe capacity' of the string is the maximum tension that it can support before it breaks. Yes, if you swing it around, the centripetal force (a real force) supplied by the tension in the string (you pull on the string, and the string pulls on the bucket) can be larger than 12 lbs and it will break.

The influence of earth's gravity has been negated

No, it hasn't. But the sum of all forces, gravity and tension, produces the motion we see.

I am therefore withdrawing from this thread
My having nothing useful or encouraging to add

How true.

 

[davedajobauk]

"By it's fruit shall a tree be known"

 

[keith99]

I appreciate how momentum is maintained, e.g. why flying insects don't get squished against the back window of the car, but as I understand it, jumping inside the station, or even decsending from the axis of rotation, would negate the momentum.

Absolutely not. The momentum remains. But the momentum is going straight, not following the curved path taken by the outside of the station. Which means a dropped ball would fall, but not fall straight, balls would behave differently if thrown upspin vrs. downspin. In some ways not unlike playing football in a wind, but with the huge exception that there is no wind to feel.

 

[whois]

Absolutely not. The momentum remains. But the momentum is going straight, not following the curved path taken by the outside of the station. Which means a dropped ball would fall, but not fall straight, balls would behave differently if thrown upspin vrs. downspin. In some ways not unlike playing football in a wind, but with the huge exception that there is no wind to feel.

the ball doesn't "fall" on the station, the floor rotates up to intercept its straight path.
it's really hard to grasp exactly the path it will take on the station, but to an observer outside the station the ball MUST travel in a straight line, and in the direction of rotation.
the above makes the assumption that you just let go, or dropped, the ball, instead of throwing it.
if you throw the ball at the right speed and angle, it's possible for the ball to travel all around the station.
this is the "stuck in mid air" scenario.
you could play catch all by yourself.

the above also makes the assumption that the station isn't orbiting anything.
i don't think the "stuck in mid air" scenario is possible on an orbiting station.

 

[keith99]

the ball doesn't "fall" on the station, the floor rotates up to intercept its straight path.
it's really hard to grasp exactly the path it will take on the station, but to an observer outside the station the ball MUST travel in a straight line, and in the direction of rotation.
the above makes the assumption that you just let go, or dropped, the ball, instead of throwing it.
if you throw the ball at the right speed and angle, it's possible for the ball to travel all around the station.
this is the "stuck in mid air" scenario.
you could play catch all by yourself.

the above also makes the assumption that the station isn't orbiting anything.
i don't think the "stuck in mid air" scenario is possible on an orbiting station.

Sure it is. In any normal (and read normal pretty much as any one that a human could survive) orbit the gravitational gradient within an orbiting station is negligible. Gravitational force does not matter it is the gradient that would matter.

 

[Strathos]

Neat thread. Where's the creationist angle?

Well a certain poster here denies that space travel exists...

 

[Oafman]

the above also makes the assumption that the station isn't orbiting anything.

Pretty much everything is orbiting something. If you leave Earth orbit, you're in solar orbit. If you leave the solar system you're in galactic orbit. The point is that any stable orbit generates a microgravity environment, so doesn't affect this discussion

 

[timewerx]

If the radius of the station was verrry large, you might not notice any difference.

If the radius is small, there will be differences in the 'gravity' experienced by your head and your feet, which would probably be disconcerting. Not to mention the fact that the curvature of the station might make it so you can't see the person you want to throw the ball to.

If the radius is really really small, if you throw a ball straight up it will turn and go either to the left or right and it won't land back to you. If you want the ball to return back to you, you'll have to throw it an angle up against the rotation of the station.

So if you're trying to throw crumpled paper with a secret message on it inside a space station with really really small rotation radius, be sure to take account the physics or it might end going to the wrong person!! Like that date you're thinking between you and the cadet might end up between you and the captain!!

 

[katerinah1947]

Hi,

Also. As we understand it, Gravity is force that does not require motion.

Centripetal, or Centrifugal forces all require motion.

So, with zero other things around, two planets a hundred thousand miles apart, are attracted to each other by a force, and will eventually hit each other.

That is not so, with force from motion.

LOVE,

 

[The Barbarian]

I always wondered how the gravity is contained once contact is lost. Imagine someone "jumping" inside a centripetal gravity station. If the jump was powerful enough to lift them off the floor, what force would overcome the upward motion and cause them to "fall"? Been wondering about that since I first read Rendezvous With Rama in the 90s.

The key here is that the floor is rotating, which means it is being constantly accelerated as it turns. So is someone standing on it. When you jump up, your intertia carries you in the direction the floor was moving at the time. But the floor is changing direction, and to you, it will appear that you fall back toward the floor for the same reason a person sitting in the back of a car making a sudden turn will feel as though they are falling toward the side of car. A floor of reasonably large radius should give you a feeling pretty much like jumping in Earth's gravity.

It's a great question, though. I'm about to speak to a Pre-AP class of middle school students, and I'm going to pose that question to them.

They should be familiar with inertia and acceleration. Should be interesting.

 

[The Barbarian]

Also. As we understand it, Gravity is force that does not require motion.

Centripetal, or Centrifugal forces all require motion.

So, with zero other things around, two planets a hundred thousand miles apart, are attracted to each other by a force, and will eventually hit each other.

That is not so, with force from motion.

They will, if they begin with no motion relative to each other, other than directly toward or directly away from each other. Here's a place to play with the idea:
https://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html

Set the slider to "accurate" and unclick "trace" to get a good look at it.

 

[The Barbarian]

The key here is that the floor is rotating, which means it is being constantly accelerated as it turns. So is someone standing on it. When you jump up, your intertia carries you in the direction the floor was moving at the time. But the floor is changing direction, and to you, it will appear that you fall back toward the floor for the same reason a person sitting in the back of a car making a sudden turn will feel as though they are falling toward the side of car. A floor of reasonably large radius should give you a feeling pretty much like jumping in Earth's gravity.

It's a great question, though. I'm about to speak to a Pre-AP class of middle school students, and I'm going to pose that question to them.

They should be familiar with inertia and acceleration. Should be interesting.

Supposedly, I can never return to a certain amusement park, because of something like this. The ride was a cylindrical room that rotated rapidly. Eventually, when the speed was great enough, the floor would lower and you'd be held against the wall. A gentle toss of a ping pong ball would return to you as if falling back to you, if you compensated for the real, vertical gravity. My sons and I discovered that tossing one across the room would make it appear to be curving.

We got applause, but the rider operator was a party pooper, it seems.

 

[whois]

Supposedly, I can never return to a certain amusement park, because of something like this. The ride was a cylindrical room that rotated rapidly. Eventually, when the speed was great enough, the floor would lower and you'd be held against the wall. A gentle toss of a ping pong ball would return to you as if falling back to you, if you compensated for the real, vertical gravity. My sons and I discovered that tossing one across the room would make it appear to be curving.

We got applause, but the rider operator was a party pooper, it seems.

maybe you and your students can book passage on a similar ride to conduct some experiments.
it would make for a great field trip, plus they could have fun and learn something too.