Centrifugal forces ' appear ' to act opposite to gravity . How is this possible?

[Mike Smith Cosmos]

I know some of the frustrations and criticisms of my ' bleating ' on about a difference with established ,proven science, causes 'Agro' or aggravation. However I must say this , ' In itself this , Is, an established scientific method ! Namely , there is a case for holding on to established understanding , and there is a case for trying to ' falsify ' existing understanding. Often, only in falsifying an existing science , does a brand new paradigm reveal itself , as an avenue for new discovery.

 

I am very , very , very , interested with new paradigms , and Blue sky research. Always have been. To me it is the ecstasy of science. To look over the hill and see a whole new 'land' . Even when it is only in ones own understanding . ('oh! Now I get it ! ' )

 

I genuinely believe such ' a new land ' beckons , just over that next hill, to do with , ( Inertia, Gravity, Singularities, Black Holes, circular motion, mass, straight lines, dark matter, and dark energy, ) . Although part of my training as an electronic engineer , included mechanical engineering as my employer once said to me as an apprentice ' you will never become a good Electronic Engineer , unless you have ,first, learned a measure of mechanical engineering" so I have had a taste of mechanical engineering. However my drive nowadays in my 'dotage' is in cross-discipline exploration , at a ' blue Sky ' level . Maybe I will see absolutely nothing . But as another famous scientist once said , "I'ts only by looking over the edge , then you ALWAYS ultimately see something ! "

 

Mike

Edited May 18, 2015 by Mike Smith Cosmos

[Strange]

Often, only in falsifying an existing science , does a brand new paradigm reveal itself , as an avenue for new discovery.

 

But falsifying established science requires evidence that contradicts that science. Your failure/refusal to understand does not constitute evidence.

 

And it is this wilful and deliberate refusal to learn that causes the "aggro" (not that there is any).

[studiot]

 

tar

 

Studiot,

 

You make an interesting point. I took my highschool physics in the late 70s. They might have taught me something that is no longer taught, because it conflicts with some results or another.

 

 

Interesting to me, because engineers and physicists had no problem building things and using things that went around in circles, when I was young. Their ideas were probably not ignorant speculations, at the time.

 

 

Thnak you for your response, tar.

 

The introduction of a fictitious centrifugal force is a valid (though currently frowned upon) method of solving certain problems in physics / engineering.

 

For instance it will enable you to calculate the tension in a string whirling with a weight on the end.

 

This is so because it reduces a dynamic problem of a system that is not in equilibrium to a static one where the system is in equilibrium.

 

However the string and weight is a particularly simple system with very few forces acting.

 

Rotodynamic machines (pumps and turbines) are much more complicated systems where the addition of a fictitious centrifugal force does not put the system into equilibrium.

In such cases D'Alembert's method is inappropriate and cannot be used to explain the workings of such machinery.

Additional forces act between the casings, the fluid and the impellors.

[swansont]

SwansonT,

 

I may have misread your account of your refreshing conversation with someone working on a problem where you pointed out an angle he was not taking into consideration, when the results did not match with what the "effect" predicted, but it sounded a little like you thought a little out of the box, he/she was confined to.

I assure you, my thinking was quite inside the box. It was a well-established effect. The colleague simply did not realize it was present.

 

But that points to the larger issue: the first place to look is inside the box, not outside, when trying to find the solution to the problem. You do not assume that physics is wrong.

 

You did not suggest physics was wrong, you just pointed out another way to look at, that would explain what was going on. You were not adding a complication, you were noticing a contributing factor to the results.

Unlike the conversations in this thread, where such behaviors abound.

 

So what are the odds that motion was completely understood 400 years ago, misunderstood 50 years ago, and understood perfectly again just recently?

 

I know I am being silly, but just making the point, that you cannot tell me SwansonT understands Newton's laws, and my Physics teacher at NJIT in the 80s had no clue. Well I suppose you can tell me I didn't understand what my teacher was saying...but that's a different point.

But that's likely the answer. It's entirely possible to explain motion using a centrifugal force term. But that's a fictitious force, to make equations looks like they follow Newton's laws. (and you have to understand what that last sentence means) It's also quite likely that the first thing a student forgets, or fails to grasp, is that the force is fictitious. That it's a bookkeeping trick.

 

One of the videos linked in this thread, started by stating we don't know what inertia is, just that bodies have a tendency, or a desire, to keep going in a straight line.

 

I think its OK to speculate on what inertia is. None here would say a force is required to keep a body going in a straight line. But there is a definite argument that a force was required to disturb the resting mass, and get it going in the first place.

Feel free. But that discussion has no place in a conversation about centripetal forces and how objects behave when traveling in uniform circular motion. Those things are quite well understood within physics.

[tar]

SwansonT,

 

I shook your martini again, but only to keep you drunk and easier to argue with.

 

My "understanding" of motion includes the inertia or the kinetic energy within a body. I understand, that in the discussions of what forces are "added" to the body in circular motion, there are only the forces accelerating it, changing its direction toward the center. However, the body does not wind up in the center, there is a tranverse, tangential effect that the kinetic energy of the body has that is countering the forces pulling toward the center. Mike and I and RobbityBob1 are not saying that physics is wrong, we are just pointing out this kinetic energy effect, like you pointed out a thing present that your collegue was not considering.

 

I do not mind musing about the new paradigms Mike talks about. Neither he nor I have any power to, or desire to change the laws of physics. What is true, will remain true, no matter what we think, or no matter what the equations say. There is always room to point out, a real effect that someone else has failed to build into the equation.

 

Regards, TAR

Edited May 18, 2015 by tar

[swansont]

SwansonT,

 

I shook your martini again, but only to keep you drunk and easier to argue with.

 

My "understanding" of motion includes the inertia or the kinetic energy within a body. I understand, that in the discussions of what forces are "added" to the body in circular motion, there are only the forces accelerating it, changing its direction toward the center. However, the body does not wind up in the center, there is a tranverse, tangential effect that the kinetic energy of the body has that is countering the forces pulling toward the center. Mike and I and RobbityBob1 are not saying that physics is wrong, we are just pointing out this kinetic energy effect, like you pointed out a thing present that your collegue was not considering.

 

I do not mind musing about the new paradigms Mike talks about. Neither he nor I have any power to, or desire to change the laws of physics. What is true, will remain true, no matter what we think, or no matter what the equations say. There is always room to point out, a real effect that someone else has failed to build into the equation.

 

Regards, TAR

 

Kinetic energy does not counteract a force. They are separate concepts. Again: start a new thread if you wish to discuss this further.

[studiot]

 

My "understanding" of motion includes the inertia or the kinetic energy within a body

 

Understanding inertia (physics answers the how but not the why) in respect of linear motion is the easy part.

 

Rotational inertia is rather more tricky.

[Mike Smith Cosmos]

At last I am on You Tube with my evidence ..

 

Here we go Link :-

 

How is that , you should see it go

 

As can be seen , by the time the tube is vertical , the lizard-with lead stuffing ,has risen to the top of the tube. It then clearly exits the tube at a near tangential trajectory. But there is a measure of radial velocity and momentum which when combined with the escape tangential velocity show a rise ABOVE the tangential line . Evidence of an acceleration , within the tube , from ' stuffed in ' position, half way down the tube , ( stationary until start of swing ) , on to the top of the tube , and external to the tube .

 

Hence , circumstantial evidence of a radial acceleration within the tube . In turn evidence of an outgoing force , along the radius of the tube . - Centrifugal . -

 

MIKE

Edited May 18, 2015 by Mike Smith Cosmos

[imatfaal]

At last I am on You Tube with my evidence ..

 

 

Or not.

"this video is private"

[studiot]

Well the dog is certainly visible.

[Mike Smith Cosmos]

Well the dog is certainly visible.

Yes but what about the escaping lizard with lead filling ! That is my evidence ! . ? Look it's rushing out of the top of the tube , partly tangential, partly vertical. Unfortunately broke my tube and scared all the dogs and babies in the vicinity!

 

 

Mike

Edited May 19, 2015 by Mike Smith Cosmos

[swansont]

And that shows a centrifugal force … how, exactly? motion ≠ force

[hypervalent_iodine]

!

Moderator Note

Closed, pending review.

[imatfaal]

Here is a tracked version - it is a still with the tube marked in blue at the moment I can first see the lizard (FFS a stuffed lizard!) and the red crosses and track are the direction in the next ten or so frames

 

 

 

[swansont]

Here is a diagram of something moving in rotating tube that is speeding up, like in the video, but the tube itself is not shown.

 

 

 

The lizard is moving at v1, and later on at v2. v2>v1 Because of the tangential motion it has, r increases. (which would happen even if v1=v2)

 

(v2-v1)/t is the acceleration. You can see that subtracting the velocity vectors points in. It would be exactly toward the center if v1=v2 (edit: and r1=r2), but is a little off of that because I have the tube's rotation accelerating. Note well that the acceleration is IN NO WAY pointed outward. There is no centrifugal acceleration. None. Nada. Zip.

 

The basic problem, I think, is that when you think of "moving along the tube" as an acceleration, but that's an analysis taking place is a reference frame that is rotating with the tube, and you are NOT ALLOWED TO DO THAT. It breaks the rules of physics. Newton's first law says that changes in velocity means there is a force, and no changes in velocity means no force. That doesn't work in a rotating frame, because you need a force to keep the object at a fixed r, with constant rotation. That means you can't go around trying to apply the definitions of acceleration and force to the problem, because Newton's first law has told you the second law doesn't work. All bets are off. (The best you can do is cook the books and add in fictitious forces, but that confuses the heck out of everyone because they forget that the books were cooked.)

 

You HAVE to analyze this from a reference frame that is not accelerating in order to apply Newton's laws and talk about forces and/or accelerations. And AFAICT everybody who is getting this wrong is trying to analyze the problem in the rotating frame. Which we know doesn't work — it will necessarily give the wrong answer.

 

You can't cite Newton's laws when Newton's laws have told you they don't apply.

[Mike Smith Cosmos]

Here is a tracked version - it is a still with the tube marked in blue at the moment I can first see the lizard (FFS a stuffed lizard!) and the red crosses and track are the direction in the next ten or so frames

 

 

Centrifugal experiment _thumbnail.jpg

 

Superimposing track of the tube in yellow and an extension of exit point ( tangential plus upward momentum ) in blue ( my blue ) .

 

 

 

This shows an increase in separation from the circle of initial tube radius , as well as an increase in radial height above exit point.

 

If it were purely tangential only , it would have been a descending half parabola from exit point.

 

The point being there was / is a radial acceleration over the time the ' lizzard' is in the tube , up the radius , of the mass.

 

Mass and acceleration of the mass sounds remarkably like m x a , which by my reckoning sounds like F , namely

 

F = m x a which is a force. Up the radius , caused by inertia as it is squeezed by the tube. Is that not so ?

 

Mike

 

 

Sorry ! Cross posted with swansont.

 

Will need to sort the two out. ( I am off to Italy tomorrow morning for ( ONE WEEK ) . Please bear with me , I will be out of wi fi range , stuck up a hillside in Umbria , where all sorts of Lizards, overrun the place. Maybe I can do more experiments over there ,with live Lizzards.

 

Mike

Here is a diagram of something moving in rotating tube that is speeding up, like in the video, but the tube itself is not shown.

 

 

 

Circ motion.png

 

The lizard is moving at v1, and later on at v2. v2>v1 Because of the tangential motion it has, r increases. (which would happen even if v1=v2)

 

(v2-v1)/t is the acceleration. You can see that subtracting the velocity vectors points in. It would be exactly toward the center if v1=v2, but is a little off of that because I have the tube's rotation accelerating. Note well that the acceleration is IN NO WAY pointed outward. There is no centrifugal acceleration. None. Nada. Zip.

 

The basic problem, I think, is that when you think of "moving along the tube" as an acceleration, but that's an analysis taking place is a reference frame that is rotating with the tube, and you are NOT ALLOWED TO DO THAT. It breaks the rules of physics. Newton's first law says that changes in velocity means there is a force, and no changes in velocity means no force. That doesn't work in a rotating frame, because you need a force to keep the object at a fixed r, with constant rotation. That means you can't go around trying to apply the definitions of acceleration and force to the problem, because Newton's first law has told you the second law doesn't work. All bets are off. (The best you can do is cook the books and add in fictitious forces, but that confuses the heck out of everyone because they forget that the books were cooked.)

 

You HAVE to analyze this from a reference frame that is not accelerating in order to apply Newton's laws and talk about forces and/or accelerations. And AFAICT everybody who is getting this wrong is trying to analyze the problem in the rotating frame. Which we know doesn't work it will necessarily give the wrong answer.

 

You can't cite Newton's laws when Newton's laws have told you they don't apply.

 

please , bear with me until I return , there may be other members who continue the conversation , while I am away!

 

Mike

Edited May 19, 2015 by Mike Smith Cosmos

[swansont]

Up the radius , caused by inertia as it is squeezed by the tube. Is that not so ?

 

 

"Up the radius" of the rotating tube in not a valid frame of reference, as I have explained. You need to use a fixed reference frame.

[Robittybob1]

Here is a diagram of something moving in rotating tube that is speeding up, like in the video, but the tube itself is not shown.

 

 

Circ motion.png

 

The lizard is moving at v1, and later on at v2. v2>v1 Because of the tangential motion it has, r increases. (which would happen even if v1=v2)

 

(v2-v1)/t is the acceleration. You can see that subtracting the velocity vectors points in. It would be exactly toward the center if v1=v2, but is a little off of that because I have the tube's rotation accelerating. Note well that the acceleration is IN NO WAY pointed outward. There is no centrifugal acceleration. None. Nada. Zip.

 

The basic problem, I think, is that when you think of "moving along the tube" as an acceleration, but that's an analysis taking place is a reference frame that is rotating with the tube, and you are NOT ALLOWED TO DO THAT. It breaks the rules of physics. Newton's first law says that changes in velocity means there is a force, and no changes in velocity means no force. That doesn't work in a rotating frame, because you need a force to keep the object at a fixed r, with constant rotation. That means you can't go around trying to apply the definitions of acceleration and force to the problem, because Newton's first law has told you the second law doesn't work. All bets are off. (The best you can do is cook the books and add in fictitious forces, but that confuses the heck out of everyone because they forget that the books were cooked.)

 

You HAVE to analyze this from a reference frame that is not accelerating in order to apply Newton's laws and talk about forces and/or accelerations. And AFAICT everybody who is getting this wrong is trying to analyze the problem in the rotating frame. Which we know doesn't work — it will necessarily give the wrong answer.

 

You can't cite Newton's laws when Newton's laws have told you they don't apply.

What is clear from my experiment and Mike's one is that as the objects go along the tubes this is a speed which will make the object leave the tube at an angle to the tangential velocity component.

I'll have to read through what you have written again later, but my experiment was done horizontally so I could ignore the force of gravity which is confounding Mike's object's trajectory.

Mike run your experiment again horizontally. Trouble becomes how do you film it then? For the best vantage point is from above it looking down.

[swansont]

What is clear from my experiment and Mike's one is that as the objects go along the tubes this is a speed which will make the object leave the tube at an angle to the tangential velocity component.

I'll have to read through what you have written again later, but my experiment was done horizontally so I could ignore the force of gravity which is confounding Mike's object's trajectory.

Mike run your experiment again horizontally. Trouble becomes how do you film it then? For the best vantage point is from above it looking down.

 

That's not related to whether there is a centrifugal force. The velocity v2 in my diagram is not fully tangential. Yet the force is inward, not out.

[pzkpfw]

What is clear from my experiment and Mike's one is that as the objects go along the tubes this is a speed which will make the object leave the tube at an angle to the tangential velocity component.

I'll have to read through what you have written again later, but my experiment was done horizontally so I could ignore the force of gravity which is confounding Mike's object's trajectory.

Mike run your experiment again horizontally. Trouble becomes how do you film it then? For the best vantage point is from above it looking down.

Swinging a pipe by hand is hardly "accurate", any odd motion on the lizard (did I write that?) is hard to pin on modern science having a misunderstanding of forces.

 

Besides, you're using tubes. That tube is itself putting forces on the object inside the tube. You've seen in the experiment with the string that gets cut, that there is no outwards motion put on the object. What's different with your tube is that the "rear" (in terms of the direction of rotation) wall of the tube is putting forces on the object (and as the tube is rotating, that force won't be directly in line with the objects momentum at any moment). That object, is trying to go in a straight line, and relative to that line the tube is giving it a slope to move along. The tube is acting as a ramp, and giving the object some momentum outwards of that straight line.

 

Even exiting the tube will have some effect. As the object gets to the end of the tube, the lip of the tube will be the last thing putting forces on the object, which itself may not be an ideal shape. That'll also have some effect on the "leaving the tube trajectory".

 

Any "outwards" component of the motion of the object, once it leaves the tube, is not evidence of centrifugal force. It's evidence of a flawed experiment.

[tar]

Mike,

 

I vote with pzkpfw for the flawed experiment.

 

When you throw the lizard it looks sort of like a lacross toss. You are doing something with the tube that looks more like a lever situation than one in which an item (lizard) is in circular motion. Besides, the lizard can never be in a situation where it is being directed by centripedal force, toward the center, because there is nothing outside the lizard in the radial direction, to constrain it, into a circular path. All you have is a little friction from the inside of the tube. Better experiment would be if you held the tube at your waist, lifted the far end about rib high, and spun yourself around like ballet dancer or iceskater doing a spin. Gravity would help hold the lizard in the midposition of the tube, and we could see if the tangential momentum translated in any way to a trek up the tube.

Besides, it would be fun to see you get dizzy and fall down, regardless of whether or not the lizard creeped up the tube, against gravity.

 

Regards, TAR

[Mike Smith Cosmos]

Mike,

 

 

Besides, it would be fun to see you get dizzy and fall down, regardless of whether or not the lizard creeped up the tube, against gravity.

 

Regards, TAR

That is exactly what I thought , as I was reading this , hell , I am going to get dizzy. The kids at school when I got them to swing a 3 Kgm weight around on the end of a 7 meter rope , on the playing field . They would , after several circles , stagger about and keel over. But they would feel something ! I would shout out " feel the force " whether they were feeling centripetal or centrifugal, they would feel a large force at the centre.

 

Mike

Edited May 19, 2015 by Mike Smith Cosmos

[swansont]

That is exactly what I thought , as I was reading this , hell , I am going to get dizzy. The kids at school when I got them to swing a 3 Kgm weight around on the end of a 7 meter rope , on the playing field . They would , after several circles , stagger about and keel over. But they would feel something ! I would shout out " feel the force " whether they were feeling centripetal or centrifugal, they would feel a large force at the centre.

Mike

Bringing in yet another scenario is probably not helpful. If you are at the center, the issue is different. You feel an outward force, because you have to exert the inward force on the mass that's moving in a circle.

[Robittybob1]

Bringing in yet another scenario is probably not helpful. If you are at the center, the issue is different. You feel an outward force, because you have to exert the inward force on the mass that's moving in a circle.

Gosh I have just had an insight of what is going on in the tube situation. It was from reading the last three posts that has inspired this.

Now think about an object in a tube starting from the center point it has one end near the center and one end further out (larger r). Now the trick is to think about the entire middle bit as a very thick string. So to begin with the two situations of a weight tied on a string inside a tube and a movable mass in the tube are the same.

Now read what Swansont said, "You feel an outward force, because you have to exert the inward force on the mass that's moving in a circle" but change that to "the central part feels an outward force, because the central part has to exert the inward force on the outer mass that's moving in a circle."

Now it is quite obvious in the "moving mass" situation that since the inner part is not tied down the inward force is less than the outward force and that imbalance continues as the mass slides along the tube.

Whereas with the string tied to the center the two forces equal each other up to the point the string can't take the strain and snaps.

Edited May 20, 2015 by Robittybob1

[DrP]

Quote: "feel the force"..

 

That force that they 'feel' is the centripetal force that they themselves are applying to the weight through the tension in the rope which gives the weight it's circular motion.... otherwise it would not go in a circle.

 

Did you watch the video? Centripetal vs Centrifugal? ALL OF IT was explained very clearly and simply in that vid.