Why do astronauts on board ISS float around

Quote from: Yendor on December 28, 2015, 09:05:40 AM

Okay, let's get back to basics. Your article talks about centripetal force and centrifugal force not being a real force. Actually, centrifugal force is what we should be talking about. I'll give you an example of centrifugal force used in everyday life, a washing machine spinning out. That is how the water in the cloths are removed. Now give me an example of centripetal force used in everyday life.

The 'tub' of the washer, being a solid connection to the center of rotation, acting on the clothes to keep them following a circular path.

Forgive me for saying, But I don't see the cloths center seeking. I see them outward seeking.

Learn how circular motion works, something can be accelerating inwards while moving in a perfect circle, basic physics. Acceleration and velocity are different things, you seem to think that inwards acceleration has to mean inwards velocity, it doesn’t.

Learn how circular motion works, something can be accelerating inwards while moving in a perfect circle, basic physics. Acceleration and velocity are different things, you seem to think that inwards acceleration has to mean inwards velocity, it doesn’t.

I'm sorry, are you addressing me?

I don't see the cloths center seeking.

Indeed.  Hence the use of centripetal force (courtesy of the wall of the tub) to make their path turn, thus following a circular path.

  I see them outward seeking.

They are trying to continue in a straight line, yes.  Just as the water is able to do courtesy of the holes in the wall of the tub.

The "centrifugal force" is the felt 'pull' of the centripetal force.

Quote from: Yendor on December 26, 2015, 02:35:53 PM

They are all floating around as if they are falling slower than the ISS is falling.

Why do you think this? If they were falling slower than the ISS is falling, they'd all be pinned to the ceiling[nb]The "ceiling" in this case is the part farthest from earth.[/nb]. But they're floating around, which is what you object to, which means they're not pinned to the ceiling.

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I was under the understanding that objects in space fall at the same rate.

All objects in space don't necessarily "fall" at the same rate, they accelerate at the same rate[nb]If they are at the same distance from the center of the Earth, in this context.[/nb]. "Falling" at the same rate means they also have the same velocity, which isn't necessarily true in all cases. Objects in the same orbit do fall at the same rate at the same point in the orbit. Objects contained within another object in orbit do meet those conditions.

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It is not obvious to me that that is true on the ISS because it looks like the spacecraft is actually falling faster than the objects inside and they never seem to catch up. I would expect to see them simply walking around normal.

Wait... if the spacecraft were always falling faster than the objects inside, unattached objects inside would be pushed against the side opposite the direction of fall. Are you seeing this? Obviously not, since you're complaining that the pictures show astronauts floating around inside it. So, how, exactly, does it "look" like this is happening? If that were happening, you would see them walking around normally, on the ceiling. Can you clarify what it is you're trying to say here because this makes no sense.

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The gravity is only about 10% less, so it can't be that. I don't see the astronauts falling slower than the ISS when they are outside tethered to the craft. They seem to be falling at the same rate or the tether would be tight. It always seem to be loose.

The acceleration of gravity, regardless of what the exact value is, is the same for both because they are at the same distance from the Earth. In this case they are falling at the same rate, so there's no net velocity between them except when the astronaut outside accelerates to maneuver around. So what you see is exactly what would be expected. Why would you expect otherwise?

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When I'm on an elevator and as it starts to go down I feel as if the floor drops out from underneath my feet, but as soon as my body catches up I don't feel it any longer.

The elevator accelerates downward from a stop for a few moments, then moves downward at a constant speed. You feel the floor drop as it accelerates, then your weight returns to normal when the acceleration stops and the downward velocity becomes constant.  This is high-school physics stuff. Consider you claim to have had a career in engineering, this is pretty disturbing since it's really, really basic and very well understood.

You never addressed any of those questions or points. Do you have any answers or comments?

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I would just expect the ISS to be the same way. I don't want anyone to get mad and start chunking more insults towards me, but this is the way I see it and I simply don't understand.

Here are what I think are the possibilities. These aren't meant to be insults, just the possibilities based on what you say here:

1) You're willing to play the foil, pretending to be ignorant, and encouraging people to present facts in a very easy to understand way. Well done! <imagine thumbs-up emoji here>

2) You just enjoy posting stuff to see what response you can elicit. Still <thumbs up>, because it elicited a lot of easy to understand explanations for anyone casually reading.

3) You really don't understand how this works, and are "exaggerating" that career in engineering. <thumbs down>, but see comment after 2), above.

4) You really don't understand how this works, but somehow managed to have a career in engineering anyway. (Yikes!    )

5) You used to be a brilliant (or at least competent) engineer and used to understand how this works but don't any more. 

Did I miss any? If not, which of these is correct? If it's 5) [I truly hope not!], it might look like 4) to you.

<The usual ad-hom attack, but no answers, no useful information.>

Nothing new here.

Quote from: Yendor on December 28, 2015, 10:43:15 AM

I don't see the cloths center seeking.

Indeed.  Hence the use of centripetal force (courtesy of the wall of the tub) to make their path turn, thus following a circular path.

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  I see them outward seeking.

They are trying to continue in a straight line, yes.  Just as the water is able to do courtesy of the holes in the wall of the tub.

The "centrifugal force" is the felt 'pull' of the centripetal force.

It is still centrifugal force pushing the cloths outward. If the clothes were forced to the center, I'd say you are right.

centripetal force is the opposite of centrifugal force. Show me something that is forced to the center of curvature of the path.

It is still centrifugal force pushing the cloths outward.

Will the clothes continue in a straight line if the tub wall were to suddenly disappear? 

If the clothes were forced to the center, I'd say you are right.

Is the tub forcing the clothes to turn from what would otherwise be a straight path?

centripetal force is the opposite of centrifugal force. Show me something that is forced to the center of curvature of the path.

Are the clothes being forced to turn from their otherwise straight path?

 Yendor

You plonker Rodney, I have explained to you all you really need to consider is Gravity Constant, Altitude and Orbital Velocity. All of  of which are identical for the ISS and the astronauts.. That Equals Equilibrium.

The astronauts are in the same frame of reference.

The  Orbital Velocity (orbital period of about 88 minutes) of  the ISS and Its crew has to be quick enough (7.66 km/s) through the very Low density atmosphere that it is traveling forwards (7.66 km/s) and falling (Gravity's effect 9.8 m/s^2) at the same rate as the Earth Curves away from it. (0.20m/km.)
The chosen Altitude for the ISS orbit was 400km above Sea Level.
The Earth is 40,075.16 kilometers round the Equator.


Test the theory,
Show me your workings
Lets find out why you believe the ISS would crash. (it would without occasional boosting)

Yendor

You plonker Rodney, I have explained to you all you really need to consider is Gravity Constant, Altitude and Orbital Velocity. All of  of which are identical for the ISS and the astronauts.. That Equals Equilibrium.

The astronauts are in the same frame of reference.

The  Orbital Velocity (orbital period of about 88 minutes) of  the ISS and Its crew has to be quick enough (7.66 km/s) through the very Low density atmosphere that it is traveling forwards (7.66 km/s) and falling (Gravity's effect 9.8 m/s^2) at the same rate as the Earth Curves away from it. (0.20m/km.)
The chosen Altitude for the ISS orbit was 400km above Sea Level.
The Earth is 40,075.16 kilometers round the Equator.


Test the theory,
Show me your workings
Lets find out why you believe the ISS would crash.

You have to rayzor in disguise.

Quote from: markjo on December 27, 2015, 04:08:53 PM

Quote from: Yendor on December 27, 2015, 02:21:40 PM

I understand what they mean by orbit. I understand that forward motion is counteracting gravity and the object will travel around the earth.

No, you obviously don't understand what they mean by orbit.  Forward motion does not counteract gravity.  Gravity is always pulling the ISS downwards.  The forward speed simply ensures that the ISS misses the earth.

Okay

Does this mean that we're making progress?

Quote from: Yendor on December 28, 2015, 07:05:00 AM

Quote from: markjo on December 27, 2015, 04:08:53 PM

Quote from: Yendor on December 27, 2015, 02:21:40 PM

I understand what they mean by orbit. I understand that forward motion is counteracting gravity and the object will travel around the earth.

No, you obviously don't understand what they mean by orbit.  Forward motion does not counteract gravity.  Gravity is always pulling the ISS downwards.  The forward speed simply ensures that the ISS misses the earth.

Okay

Does this mean that we're making progress?

Yes, I believe we are. Thanks for asking.

Quote from: Yendor on December 28, 2015, 11:48:20 AM

It is still centrifugal force pushing the cloths outward.

Will the clothes continue in a straight line if the tub wall were to suddenly disappear? 

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If the clothes were forced to the center, I'd say you are right.

Is the tub forcing the clothes to turn from what would otherwise be a straight path?

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centripetal force is the opposite of centrifugal force. Show me something that is forced to the center of curvature of the path.

Are the clothes being forced to turn from their otherwise straight path?

All yes and you just described centrifugal force. Again, please show me something that is pulled to the center of curvature of the path.

https://en.wikipedia.org/wiki/Centripetal_force

Are you are saying if I drive a car fast around a racetrack that the car will try to go towards the center of the track instead of towards the outside of the track? I've never seen that. I've only seen them being pushed towards the outside of the track.

Quote from: frenat on December 28, 2015, 12:37:42 PM

https://en.wikipedia.org/wiki/Centripetal_force

Are you are saying if I drive a car fast around a racetrack that the car will try to go towards the center of the track instead of towards the outside of the track? I've never seen that. I've only seen them being pushed towards the outside of the track.

I'm saying only that I linked a page describing centripetal force.  Do try to avoid putting words in my mouth.

the page linked says the force is orthogonal to the motion.

The way I've seen it described is when you accelerate in a straight line the force is forwards but you feel pushed back in your seat.  Similarly when turning in a circle you feel pushed to the outside but the force is opposite towards the center.

A force creates acceleration, not velocity, an inwards force for creates an inwards acceleration, but there is enough velocity to keep the car/clothes/iss in a circler path.

Quote from: 29silhouette on December 28, 2015, 12:09:51 PM

Is the tub forcing the clothes to turn from what would otherwise be a straight path?

Are the clothes being forced to turn from their otherwise straight path?

All yes and you just described centrifugal force.

Not on the last two.  The clothes would simply continue in a straight path.  They are being forced to turn inward, which you just agreed with, and you have stated centripetal force is the opposite of centrifugal.

Again, please show me something that is pulled to the center of curvature of the path.

I did.

Quote from: 29silhouette on December 28, 2015, 11:02:45 AM

The "centrifugal force" is the felt 'pull' of the centripetal force.

It is still centrifugal force pushing the cloths outward. If the clothes were forced to the center, I'd say you are right.

Since you have agreed they are being forced to turn inward, thus following a circle instead of continuing straight, then I guess I'm right, and now surely you must understand what centripetal force is.  Yes or no?

Quote from: Yendor on December 28, 2015, 12:35:59 PM

Quote from: 29silhouette on December 28, 2015, 12:09:51 PM

Is the tub forcing the clothes to turn from what would otherwise be a straight path?

Are the clothes being forced to turn from their otherwise straight path?

All yes and you just described centrifugal force.

Not on the last two.  The clothes would simply continue in a straight path.  They are being forced to turn inward, which you just agreed with, and you have stated centripetal force is the opposite of centrifugal.

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Again, please show me something that is pulled to the center of curvature of the path.

I did.

Quote from: Yendor on December 28, 2015, 11:48:20 AM

Quote from: 29silhouette on December 28, 2015, 11:02:45 AM

The "centrifugal force" is the felt 'pull' of the centripetal force.

It is still centrifugal force pushing the cloths outward. If the clothes were forced to the center, I'd say you are right.

Since you have agreed they are being forced to turn inward, thus following a circle instead of continuing straight, then I guess I'm right, and now surely you must understand what centripetal force is.  Yes or no?

The cloths are forced by the tub to turn inward the same as centrifugal. A ball on a string twirling over your head is centrifugal force pushing the outwards. If i let out some more string the ball will take up the slack and move further out. If when I let out more string the ball came closer to the center, that would be the opposite to  centrifugal force, centripetal force. Show me something that works like that.

No, centripetal force is in all of those examples as the inwards acceleration that causes the object to turn. The centrifugal force only appears in the reference frame of the object, take an ant standing on the ball, it would fell an outwards centrifugal force.

No, centripetal force is in all of those examples as the inwards acceleration that causes the object to turn. The centrifugal force only appears in the reference frame of the object, take an ant standing on the ball, it would fell an outwards centrifugal force.

If the ant is on the ball as it spins round he would feel an outward force and it would be called centrifugal force. In that case the ones inside and outside the ISS are feeling centrifugal force as well.

Yes, but less than we feel on earth, and even that's small.

The cloths are forced by the tub to turn inward the same as centrifugal.

The force of the tub wall causing the clothes to turn inward is centripetal.

A ball on a string twirling over your head is centrifugal force pushing the outwards.

Nothing is trying to push the ball outward, it's merely trying to travel in a straight path, which would be away from the center of it's circular path. 

If i let out some more string the ball will take up the slack and move further out.

As the centripetal force is lessened, yes the ball will move further out as it tries to go straight momentarily.

If when I let out more string the ball came closer to the center, that would be the opposite to  centrifugal force, centripetal force.

How would the ball come closer by letting out more string?  The centripetal force is what is making the ball follow it's circular path.  Pulling the string in would make the ball come closer to center.

Show me something that works like that.

A ball on a string.  Centripetal force makes it turn instead of going straight.

Or, do you want to see something that, when centripetal force is lessened or removed, curves inward even more instead of straightening out?

Quote from: Yendor on December 28, 2015, 02:05:36 PM

The cloths are forced by the tub to turn inward the same as centrifugal.

The force of the tub wall causing the clothes to turn inward is centripetal.

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A ball on a string twirling over your head is centrifugal force pushing the outwards.

Nothing is trying to push the ball outward, it's merely trying to travel in a straight path, which would be away from the center of it's circular path. 

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If i let out some more string the ball will take up the slack and move further out.

As the centripetal force is lessened, yes the ball will move further out as it tries to go straight momentarily.

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If when I let out more string the ball came closer to the center, that would be the opposite to  centrifugal force, centripetal force.

How would the ball come closer by letting out more string?  The centripetal force is what is making the ball follow it's circular path.  Pulling the string in would make the ball come closer to center.

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Show me something that works like that.

A ball on a string.  Centripetal force makes it turn instead of going straight.

Or, do you want to see something that, when centripetal force is lessened or removed, curves inward even more instead of straightening out?

Okay, I believe we are on the right track about this. Let me show you what I found on the internet.

A piece of string with ball attached to one of the ends is held firmly by the hand. An impulse or motion is imparted to the ball by the hand, that motion being continued by the movement from the hand. The first impulse given to the ball by the hand represents the Primitive Impulse. The tension on the string which holds the ball to its controlling centre represents the Centripetal Force, while the opposite force on the string, which takes up the Primitive Impulse and continues it, is represented by the Centrifugal Force.

In other words, a ball with a string attached hanging from your hand by the string is the Centripetal Force because the string is putting a force on the ball to keep it in the center or in your hand in this case. Now when you give the string and ball motion and the ball twirls around over your head that is Centrifugal Force because it is a force pulling the ball away from the center or your hand in this case. The string is supplying the Centripetal Force and the ball twirling is supplying the Centrifugal Force. These two forces work exactly opposite each other.

Now, I can understand this.

So the reason why astronauts float in space is due to centripetal/centrifugal? force or falling around the Earth at super speed?

Would this be right and if so, what else can make astronauts float in space?

So the reason why astronauts float in space is due to centripetal/centrifugal? force or falling around the Earth at super speed?

Basically, yes. They have no net motion relative to nearby objects because they're all traveling and accelerating in the same direction at the same rate.

Would this be right and if so, what else can make astronauts float in space?

Witches!    [nb]I'm including the little winky symbol so I can be sure you know I'm kidding here. I don't really believe witches can make astronauts float in space. It's a joke.[/nb]
 

Quote from: sceptimatic on January 08, 2016, 08:40:41 AM

So the reason why astronauts float in space is due to centripetal/centrifugal? force or falling around the Earth at super speed?

Basically, yes. They have no net motion relative to nearby objects because they're all traveling and accelerating in the same direction at the same rate.

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Would this be right and if so, what else can make astronauts float in space?

Witches!    [nb]I'm including the little winky symbol so I can be sure you know I'm kidding here. I don't really believe witches can make astronauts float in space. It's a joke.[/nb]

Maybe you can tell me why the Apollo astronauts were floating inside their craft when out of Earth's so called orbit?

Also as an added extra, how did the so called Apollo craft actually fly to the so called moon when it wasn't orbiting Earth and was on a supposed straight trajectory towards the so called moon, meaning it had no means to float and can't have used propulsion.

Now before you go into this, " an object in motion will stay in motion until acted upon by an opposite force" you have to tell me how this craft floated, bearing in mind that there is no up/down/side to side in so called space and is a so called vacuum or nothingness.

Let's see what you can come back with before I proceed.

Apollo was in orbit around the earth. The trans lunar injection pushed the spacecraft into an elliptical orbit that intersects the moon.

Apollo was in orbit around the earth. The trans lunar injection pushed the spacecraft into an elliptical orbit that intersects the moon.

Well let's see if we can clear a few things up.
I recall Gene Cernan mention that they orbited the Earth about one and a half times, then off on a trajectory towards the moon.
Ok, I can accept this bit for the sake of it.
How fast was the orbit around the Earth for that one and a half times?...any idea?

Quote from: Mainframes on January 08, 2016, 09:54:13 AM

Apollo was in orbit around the earth. The trans lunar injection pushed the spacecraft into an elliptical orbit that intersects the moon.

Well let's see if we can clear a few things up.
I recall Gene Cernan mention that they orbited the Earth about one and a half times, then off on a trajectory towards the moon.
Ok, I can accept this bit for the sake of it.
How fast was the orbit around the Earth for that one and a half times?...any idea?

It was a couple of hours if I recall correctly.