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Offline jerrygg38

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What is centrifugal force?
« on: 14/08/2016 19:21:31 »
What is centrifugal force?
  In the previous discussion Alancalverd stated that there was no such thing as centrifugal force. Thus it is just a way of expressing the resultant force tending to push an object away from a string or a gravitational force. It appears that there are two different but similar cases. In the case of a string, the object spinning around a center point wants to go in a straight line. The string prevents this and you end up with a vector problem in which the string has actual centripetal force acting from the center point. This is just simple mechanical engineering 101.
  Now let us look at the Earth spinning around the sun. For simplicity we can say that the ellipse is basically a circle although the equations are the similar. There is no longer a string between the earth and the sun. The simple vector forces of the spinning ball on a rope do not apply but the answers are basically the same. Thus we can say that we have a gravitational centripetal force and a gravitational centrifugal force. This is a much more complex scientific problem.  Since there is no rope between sun and earth, space itself must act to produce the force of attraction.
  However it is not really possible to conceive that space produces an attractive force. The only explanation is that space pushes the Earth and sun together. Einstein produced his general relativity equations to account for the action of space upon the sun and Earth. The pushing together of earth and sun is self-evident to me. So there is no such thing as centripetal force. It is just a mathematical tool.
   Then we are left with centrifugal force. The earth and sun interact by their gravitational fields.  As the earth moves around the sun the earth wants to move in a straight line. At the same time the two gravitational fields tend to combine and set up a combined center. These fields exist further out in space and the net result is the earth is pushed toward the sun and visa-versa. At the same time the sun wobbles around its axis since the center of gravity of the earth/sun combination keeps moving.  Of course the other planets make the wobble of the sun more complex.
  As the Earth moves in a linear fashion and is pushed toward the sun, the earthís gravitational field tends to push against the sunís gravitational field. This causes the combined field to look like a circular railroad track. The static fields tend to push the earth toward the sun but the dynamic fields tend to push the earth away from the sun.
  We then have the centripetal force due to the static gravitational forces which tend to bring both earth and sun to a common center point and the centrifugal forces which are dynamic and tend to push the earth away from the sun. These equal and opposite forces then are very similar to the ball and string problem.
    Anyway the previous response by Alancaverd got me to thinking about the centrifugal force. What do you guys think of this analysis?


 
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Offline alancalverd

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Re: What is centrifugal force?
« Reply #1 on: 15/08/2016 23:13:07 »
I never said it didn't exist! I'm a scientist, for heaven's sake, not a writer of science textbooks!

Centrifugal force is what separates liquids in a centrifuge. If there was only a centripetal force, the liquid would all rise out of the test tube and splash around  in the middle of the machine. Centrifugal force is what keeps "wall of death" riders stuck to the inside of the cage instead of collapsing in a heap at the bottom. Whan yo black out in a high-g turn, is it because your head is being pulled into the middle of the turn, or because your blood is being squeezed outwards? Does the centripetal force shrink the wheel, or does the centrifugal force expand the tyre? It is the radial outward force on a body that follows a curved path.

If you whirl a stone around on a string, you can feel the outward tension in the string. It must be outward because a string can't push, any more than a liquid can pull.

Idiot textbook writers say "but if you cut the string, the stone moves at a tangent, not a radius, so there can't be a radial force". I say "if you cut the string, the stone is no longer constrained to move in a curved path, so Newton's first law applies - the body continues to move in a straight line, which is obviously the tangent at the point of cutting."

This is the kind of nonsense that pays philosphers' salaries, and should therefore be banned from polite conversation.
 
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Offline jerrygg38

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Re: What is centrifugal force?
« Reply #2 on: 16/08/2016 11:13:12 »
I never said it didn't exist! I'm a scientist, for heaven's sake, not a writer of science textbooks!

Centrifugal force is what separates liquids in a centrifuge. If there was only a centripetal force, the liquid would all rise out of the test tube and splash around  in the middle of the machine. Centrifugal force is what keeps "wall of death" riders stuck to the inside of the cage instead of collapsing in a heap at the bottom. Whan yo black out in a high-g turn, is it because your head is being pulled into the middle of the turn, or because your blood is being squeezed outwards? Does the centripetal force shrink the wheel, or does the centrifugal force expand the tyre? It is the radial outward force on a body that follows a curved path.

If you whirl a stone around on a string, you can feel the outward tension in the string. It must be outward because a string can't push, any more than a liquid can pull.

Idiot textbook writers say "but if you cut the string, the stone moves at a tangent, not a radius, so there can't be a radial force". I say "if you cut the string, the stone is no longer constrained to move in a curved path, so Newton's first law applies - the body continues to move in a straight line, which is obviously the tangent at the point of cutting."

This is the kind of nonsense that pays philosphers' salaries, and should therefore be banned from polite conversation.
  Thanks for the clarification of your beliefs. You had said ""Modern" textbooks insist that there is no such thing as centrifugal force.

This is a great comfort to mechanical engineers, who can now spin wheels as fast as they like without the tyres coming off or the grinding wheel bursting.

It is however worrying to know that the tension you feel when you whirl an object around on a string, or the phenomenon that makes you black out in a tight aerobatic turn (just before the wings fall off)  is a figment of your outdated imagination. "

   Your words had confused me as to your beliefs. Now you clarified them so you believe that the modern textbook writers are idiots in their beliefs. I had never read a modern textbook as most of my studies involved my old textbooks and whatever new data I got from the internet or various articles.
  So now I am still left with wondering why the writers of the textbooks believe that centrifugal force does not exist.
   The rope and the string doesn't need a centrifugal force because the sting constrains the motion of the length of the string. In this case the centrifugal force does not have to exist but is merely a vector caused by the momentum of the ball and the length of the string.
  The earth spinning around the sun is different. There is no string so the centrifugal force is not easily identified. You have a momentum and a gravitational pressure pushing the earth toward the sun. What keeps the earth from falling into the sun?  That is the big problem.
  So we get a law of physics such that "A planet moving with velocity V tangent to the radius from a star will generate a centrifugal force that balances the centripetal force and this keeps the planet from falling into the star".
  The question is why does this law happen. To say it happens is fine. It is just a law. But as an engineer I want to understand why it happens.
 From an electrical perspective we could say that the planets gravitational field cuts the stars gravitational field and this produces a gravitational gradient vector. Thus the centrifugal force is an induced gravitational field that is equal and opposite to the main gravitational field attraction.
   As I look at the moon and the earth, it is self evident to me that the moon is phase locked to the Earth. This is an electrical type term. The Earths gravitational field is cutting the moon and producing eddy type gravitational currents within the moon. This slowly brings the moon to a standstill and we only see one face of the moon.
  The question is whether Einstein and others have considered what happens when one gravitational field cuts another field during orbital motion? Do gravitational eddy currents exist? I believe they do. What do you think?
 

Online Colin2B

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Re: What is centrifugal force?
« Reply #3 on: 17/08/2016 09:01:41 »
Many textbooks only give half the story. The interesting thing about forces like centrifugal and Coriolis is that they are frame dependant. From an inertial frame there is no force but just the relative movement of two objects. However, from the rotating frame - the car on a bend, the child on the roundabout, the tension in the string - the force is very real and obvious.
 

Offline jeffreyH

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Re: What is centrifugal force?
« Reply #4 on: 17/08/2016 10:43:57 »
In simplistic terms F = ma. A change in vector direction is an acceleration. Therefore you have a force. Why the confusion?
 

Offline jerrygg38

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Re: What is centrifugal force?
« Reply #5 on: 19/08/2016 12:08:00 »
In simplistic terms F = ma. A change in vector direction is an acceleration. Therefore you have a force. Why the confusion?
   That is true. But the questions is why? What is the physical mechanism that produces the force? Mathematical laws are nice but do we live in a mathematical universe or a physical universe?  If we live in a mathematical universe then the above equation is fine. If we live in a physical universe then what is the physical reason for centrifugal force.
  So if we look at a spinning mass such as  planet Saturn we find rings that are spinning around in a plane. The rings are held by gravity and counterbalanced by centrifugal force.
  Two things are at play. There is the mass of Saturn and the gravitational field of Saturn. For this case the effect of the sun or other planets is small. The centrifugal force acting upon the rings is an interaction between the small gravitational fields of all the tiny particles and the larger gravitational field of Saturn.
   As I see it, the physical reason for the centrifugal force is due to the motion of the tiny particle fields and the larger field of Saturn. The mathematical law may be fine but the reason for the law is a more complex field problem. what do you think?
 

Offline PhysBang

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Re: What is centrifugal force?
« Reply #6 on: 19/08/2016 12:44:18 »
This is the kind of nonsense that pays philosphers' salaries, and should therefore be banned from polite conversation.
There are many philosophers that can do physics far, far better than you, so perhaps you should refrain from attacking philosophers in general.

The reason that people say that there is no centrifugal force is that there is no source for the force other than the centripetal force involved and inertia.
In simplistic terms F = ma. A change in vector direction is an acceleration. Therefore you have a force. Why the confusion?
In this case, the the vector decomposition is into inertia and centripetal force, there is no separate centrifugal source.
 

Offline jeffreyH

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Re: What is centrifugal force?
« Reply #7 on: 19/08/2016 13:06:02 »
This is the kind of nonsense that huh uh pays philosphers' salaries, and should therefore be banned from polite conversation.
There are many philosophers that can do physics far, far better than you, so perhaps you should refrain from attacking philosophers in general.

The reason that people say that there is no centrifugal force is that there is no source for the force other than the centripetal force involved and inertia.
In simplistic terms F = ma. A change in vector direction is an acceleration. Therefore you have a force. Why the confusion?
In this case, the the vector decomposition is into inertia and centripetal force, there is no separate centrifugal source.

Define the system(s) for which this is true.
 

Offline jerrygg38

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Re: What is centrifugal force?
« Reply #8 on: 19/08/2016 15:40:32 »

The reason that people say that there is no centrifugal force is that there is no source for the force other than the centripetal force involved and inertia.

  I just posted my understanding of :Why does a mass move in a straight line and with constant velocity"  in new theories which should help to explain the centrifugal force. In my latest thoughts It is a force due to the motion of an object in relation to its own gravitational field.
 

Offline alancalverd

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Re: What is centrifugal force?
« Reply #9 on: 20/08/2016 00:09:26 »
Quote
There are many philosophers that can do physics far, far better than you, so perhaps you should refrain from attacking philosophers in general.
I am flattered that you know how good I am, and surprised that you did not name a philosopher who can do my job better - the profession is not known for modesty.

Quote
The reason that people say that there is no centrifugal force is that there is no source for the force other than the centripetal force involved and inertia.
which is why nobody blacks out during aerobatics, and tyres do not come off wheels at high speed? In my universe, something is opposing the arterial flow to my brain and some outward force is expanding the tyres.
« Last Edit: 20/08/2016 00:26:07 by alancalverd »
 

Offline jerrygg38

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Re: What is centrifugal force?
« Reply #10 on: 20/08/2016 11:42:39 »
AlanCalverd said about centrifugal force
"which is why nobody blacks out during aerobatics, and tyres do not come off wheels at high speed? In my universe, something is opposing the arterial flow to my brain and some outward force is expanding the tyres."
  It is easy to spin a ball on a string and feel the pull. Likewise when you drive your car on a curve you can feel the results. In addition they bank the curves on racetracks to prevent the cars from going out of control. To me it appears that the centrifugal force is an actual force rather than a resultant vector of linear motion and a perpendicular attractive force. Perhaps the resulting force is the result of the cutting of the earths gravitational field by the moving objects gravitational field. Then we get two different ways of looking at the same problem. One would think that the mathematicians would have come up with this type of analysis already.
 

Offline puppypower

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Re: What is centrifugal force?
« Reply #11 on: 20/08/2016 12:00:24 »
In a Newtonian sense, for every action there is a reaction. Centrifugal force appears to be a reactive force, to a constraining force, that is acting perpendicular to the direction of velocity.

In terms of relativity, gravity as defined by General Relativity, causes space-time to curve. In the case of an orbit, is the centrifugal force a reaction to GR and the curvature of space-time? If we orbited a neutron star, we would feel the centrifugal force.

If we have a weight on a string being moved in an orbit, a restraining force is causing the velocity to accelerate; change direction. This is felt as centrifugal force. If we cut the string, to remove the restraining force, the weigh continues on in straight line. If the restraining force was gravity; GR, is the straight line implicit of zero curvature space-time?

We use the moons and planets to sling shot satellites to distant planets. We make use of the centrifugal force, returning the probe to zero curvature space-time, between the centrifugal force induced by the GR of each planet or moon. Does velocity use an absolute reference of zero space-time curvature, if the centrifugal force is zero; string is cut?

Velocity is d/t, while acceleration is d/t/t. The centrifugal force contains extra units of time; potential, relative to velocity. When this time potential is zero, there is no curvature in space-time; pure velocity.
 

Offline jerrygg38

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Re: What is centrifugal force?
« Reply #12 on: 20/08/2016 14:27:38 »
In a Newtonian sense, for every action there is a reaction. Centrifugal force appears to be a reactive force, to a constraining force, that is acting perpendicular to the direction of velocity.

In terms of relativity, gravity as defined by General Relativity, causes space-time to curve. In the case of an orbit, is the centrifugal force a reaction to GR and the curvature of space-time?
Velocity is d/t, while acceleration is d/t/t. The centrifugal force contains extra units of time; potential, relative to velocity. When this time potential is zero, there is no curvature in space-time; pure velocity.

  The problem with your words is that you say General
Relativity causes space time to curve. How can general relativity cause space time to curve? Why? This makes no sense. Somehow there is a Sky God called "general relativity" that causes planets and photons, etc. to move in curved paths. This is pure magic and very unscientific for sure. The mathematicians may be happy so say such things but as an Engineer I do not believe it. To be more truthful, general relativity is a mathematical theory which is able to accurately calculate measurements of the universe. Thus it is a true mathematical approximation to reality. However general relativity causes nothing at all. Thus the answers I seek is to understand why Einsteins math works well.
 

Offline PhysBang

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Re: What is centrifugal force?
« Reply #13 on: 20/08/2016 14:58:18 »
In simplistic terms F = ma. A change in vector direction is an acceleration. Therefore you have a force. Why the confusion?
   That is true. But the questions is why? What is the physical mechanism that produces the force? Mathematical laws are nice but do we live in a mathematical universe or a physical universe?  If we live in a mathematical universe then the above equation is fine. If we live in a physical universe then what is the physical reason for centrifugal force.
  So if we look at a spinning mass such as  planet Saturn we find rings that are spinning around in a plane. The rings are held by gravity and counterbalanced by centrifugal force.
  Two things are at play. There is the mass of Saturn and the gravitational field of Saturn. For this case the effect of the sun or other planets is small. The centrifugal force acting upon the rings is an interaction between the small gravitational fields of all the tiny particles and the larger gravitational field of Saturn.
   As I see it, the physical reason for the centrifugal force is due to the motion of the tiny particle fields and the larger field of Saturn. The mathematical law may be fine but the reason for the law is a more complex field problem. what do you think?
This is so horribly wrong. The rings are held in place by centripetal force.
 

Offline PhysBang

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Re: What is centrifugal force?
« Reply #14 on: 20/08/2016 14:59:05 »
Define the system(s) for which this is true.
Define?

I can tell you the ones for which they are true: every planet in the solar system. Every galaxy.
 

Offline jeffreyH

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Re: What is centrifugal force?
« Reply #15 on: 20/08/2016 15:39:31 »
Define the system(s) for which this is true.
Define?

I can tell you the ones for which they are true: every planet in the solar system. Every galaxy.

Ok so we can define gravitation as a system with no centrifugal force. Any others?
 

Offline PhysBang

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Re: What is centrifugal force?
« Reply #16 on: 20/08/2016 18:11:31 »
Ok so we can define gravitation as a system with no centrifugal force. Any others?
I don't think you get it.

The great theory of Newton on gravity is that what holds the planets in orbit is the force of gravity acting on them directing them towards, roughly, the sun.

Centrifugal force is the force supposedly directed outwards away from the center due to rotation. This is, in all cases, due to the equal and opposite reaction of being diverted towards a center from otherwise linear motion.
 

Offline jeffreyH

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Re: What is centrifugal force?
« Reply #17 on: 20/08/2016 18:17:41 »
Ok so we can define gravitation as a system with no centrifugal force. Any others?
I don't think you get it.

The great theory of Newton on gravity is that what holds the planets in orbit is the force of gravity acting on them directing them towards, roughly, the sun.

OK that's the centripetal force.

Quote
Centrifugal force is the force supposedly directed outwards away from the center due to rotation. This is, in all cases, due to the equal and opposite reaction of being diverted towards a center from otherwise linear motion.

OK So define systems not related to gravity.
 

Offline PhysBang

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Re: What is centrifugal force?
« Reply #18 on: 20/08/2016 18:56:20 »
OK So define systems not related to gravity.
You keep using the word "define", but I don't think it means what you think it means.

Think of the device called a "centrifuge". This device spins and imparts a linear velocity on the contents of the vessel(s) in the device, but the contents are diverted from their course by the electromagnetic forces holding the device in its solid form.
 

Offline jeffreyH

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Re: What is centrifugal force?
« Reply #19 on: 20/08/2016 19:14:00 »
OK So define systems not related to gravity.
You keep using the word "define", but I don't think it means what you think it means.

Think of the device called a "centrifuge". This device spins and imparts a linear velocity on the contents of the vessel(s) in the device, but the contents are diverted from their course by the electromagnetic forces holding the device in its solid form.

This is not a trivial point. We have a definition of ficticious or pseudo force which covers centrifugal force. I have seen it stated at times that gravity is a fictitious force. That magical changes in geometry cause gravity. Therefore I believe it is important to nail down a definition.
 

Offline jerrygg38

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Re: What is centrifugal force?
« Reply #20 on: 20/08/2016 19:39:02 »
Ok so we can define gravitation as a system with no centrifugal force. Any others?
I don't think you get it.

The great theory of Newton on gravity is that what holds the planets in orbit is the force of gravity acting on them directing them towards, roughly, the sun.

Centrifugal force is the force supposedly directed outwards away from the center due to rotation. This is, in all cases, due to the equal and opposite reaction of being diverted towards a center from otherwise linear motion.
  The equal and opposite reaction may be true but what does it mean? Centrifugal force is equal and opposite to centripetal force is something we can memorize but it lacks meaning. What is the mechanism by which it is true? The basic understanding of physics is lacking. All we have are rules to remember. And I for one want to know why!
 

Offline hamdani yusuf

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Re: What is centrifugal force?
« Reply #21 on: 24/08/2016 02:19:21 »
Ok so we can define gravitation as a system with no centrifugal force. Any others?
I don't think you get it.

The great theory of Newton on gravity is that what holds the planets in orbit is the force of gravity acting on them directing them towards, roughly, the sun.

Centrifugal force is the force supposedly directed outwards away from the center due to rotation. This is, in all cases, due to the equal and opposite reaction of being diverted towards a center from otherwise linear motion.
  The equal and opposite reaction may be true but what does it mean? Centrifugal force is equal and opposite to centripetal force is something we can memorize but it lacks meaning. What is the mechanism by which it is true? The basic understanding of physics is lacking. All we have are rules to remember. And I for one want to know why!
Centrifugal force emerges when there are strength difference in centripetal forces working on parts of a system.
In a turning moving car, the road forces the wheels sideway which in turn forces other parts of the car which is then felt by the passengers. The passengers don't receive any force directly from the road.
In ISS, the earth forces each part almost equally, including every atoms of its passengers. That's why they don't feel the centrifugal force even though centripetal force done by the earth to them through gravity is comparable to the turning car.
 

Offline PmbPhy

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Re: What is centrifugal force?
« Reply #22 on: 24/08/2016 13:25:42 »
Quote from: jerrygg38
What is centrifugal force?
Simply put, centrifugal force is an inertial force. If you're at rest in a rotating frame of reference then objects which are moving with no acceleration in the inertial frame will accelerate in your frame.

You can read more about inertial forces on my website at:
http://www.newenglandphysics.org/physics_world/gr/inertial_force.htm
 

Offline jerrygg38

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Re: What is centrifugal force?
« Reply #23 on: 24/08/2016 14:15:04 »
hamdani yusuf said:
In ISS, the earth forces each part almost equally, including every atoms of its passengers. That's why they don't feel the centrifugal force even though centripetal force done by the earth to them through gravity is comparable to the turning car.
You raise an interesting point. Why don't we feel the rotation of the Earth? You say that everything upon the earth has equal forces on it. In other words, you need differential forces to feel the centrifugal force.
Thus the Earth itself has a centrifugal force relative to the sun. It may be that our atmosphere acts a counterbalance to our centrifugal forces. If the Earth spun faster and faster each second, then perhaps we would notice this force.
   In the space station, they are moving fast but they do not experience being pushed against the outer side of the cabin. Thus again they are subject to the same force as the space station but they are inside the station. So they feel nothing. The space station as a whole feels the centrifugal force.
 
 

Offline jerrygg38

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Re: What is centrifugal force?
« Reply #24 on: 24/08/2016 14:23:39 »
To all:
  It seems to me at the moment that centrifugal force is similar to the force that occurs when you try to rotate a gyroscope slightly perpendicular to its axis. It is beginning to seem to me that it is not a fancy space time force but a simple internal force that originates within the object itself. Any other ideas from the world of science?
 

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Re: What is centrifugal force?
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