Jump to content

Swinging the Lead - Debunking Centrifugal Force


Recommended Posts

Heat only flows from hot(ter) to colder. Look up entropy.  If OME's right about certrifugal force, my pushbike needs no mudguards and I must look for some other reason by person gets covered in road grit. Nev

Link to post
Share on other sites
  • Replies 53
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

This post comes with no guarantees but this is what I remember of this subject.     I haven't yet looked this up and I am more than happy to be contradicted     If we have a ball on a p

You're a little bit fixated, aren't you OME? I'm tempted to slip the word "centrifugal" into more posts... 😈

OME is dissecting the semantics of a generally accepted simplified term for an observable effect. It's a lot more confusing to say 'accelerating sideways whilst travelling along an arc, without c

Posted Images

14 minutes ago, facthunter said:

OME's right about certrifugal force, my pushbike needs no mudguards and I must look for some other reason by person gets covered in road grit. Nev

Why don't you take the time to watch the video I just posted? It explains why you get a black stripe up your back if your bike doesn't have a rear mudguard.

Link to post
Share on other sites

If heat only flows from hotter to colder, how come if you put a hot object into a bowl of cold water for 5 minutes and then pull it out won't you find that its temperature is lower. That to me says the cold has travelled to the hot object. What has really happened is that everything tries to be in equilibrium.

Which is the same as the suck, blow argument and the centrifugal, centripetal argument.

It is really an argument about the meaning of words, which do not mean what we think they mean, but they do make sense to us, so they work OK.

  • Like 1
Link to post
Share on other sites
8 minutes ago, facthunter said:

Heat only flows from hot(ter) to colder. Look up entropy.  If OME's right about certrifugal force, my pushbike needs no mudguards and I must look for some other reason by person gets covered in road grit. Nev

That is a good example.  the mud is stuck to the wheel. the wheel imparts motion to the mud. The mud has no option but to follow the circular path of the wheel. What the mud wants to do is travel in a straight line due to inertia.   The faster the wheel turns the more inertia there is.  The mud wants to travel in a straight line but cant because of its adhesion to the wheel. Once the wheel and thus the mud is traveling fast enough the muds need to travel in a straight line will seperate it from the wheel. It will then travel, freed of the rotating force of the wheel continue to travel in a straight line (inertia)

 

If we are in a car and it travels around a bend we will feel like we are being pulled in the opposite direction to the bend but in fact our body wants to keep travelling in a straight line but the seat and side of the car is pushing against this tendency. 

  • Thanks 1
Link to post
Share on other sites

 Cold doesn't exist. It's what is there when there's NO heat. It's NOT just a matter of how you look at it..  minus 273 C is absolute zero. ie 0 degrees KELVIN. You cannot go any colder as atoms cease to vibrate and things become superconductors. I doubt there's an absolute upper limit. Nev

  • Like 1
Link to post
Share on other sites

No Nev. You've missed the most important part of your own comparison.

'Cold' is not what's left when the heat goes away. 'Cold' (like centrifugal force) does not exist. 'Heat'is what exists. We use the word 'cold' to describe the lack of heat energy.

  • Like 1
Link to post
Share on other sites

OME is dissecting the semantics of a generally accepted simplified term for an observable effect.

It's a lot more confusing to say 'accelerating sideways whilst travelling along an arc, without changing instantaneous forward velocity', when one can say 'centrifugal force'.

  • Like 1
Link to post
Share on other sites

That's taking my post a bit too far, OME.

I don't think I cast any doubt upon the aparrent direction of the sun's travel across our skies.

 

But I do suggest that you are creating a scientific debate about the semantics of 'centrifugal' force.

Link to post
Share on other sites
1 hour ago, nomadpete said:

I don't think I cast any doubt upon the aparrent direction of the sun's travel across our skies.

No. My question was aimed at eliciting responses that would indicate if the responder held the view that the Universe was geocentric or heliocentric. Based on that answer, I intended to make further comment.

 

1 hour ago, nomadpete said:

 

But I do suggest that you are creating a scientific debate about the semantics of 'centrifugal' force

"Centrifugal" and "Centripetal" are acceptable words in the language. Each word has a clear, concise definition and etymology.

 

Centrifugal: flying off or proceeding out from a centre," 1690s, with adjectival suffix -al (1) + Modern Latin centrifugus, 1687, coined by Sir Isaac Newton in "Principia", from Latin centri-, alternative combining form of centrum "centre"  + fugere "to flee" . Centrifugal force is Newton's vis centrifuga. flying off or proceeding out from a centre," 1690s, with adjectival suffix -al (1) + Modern Latin centrifugus, 1687, coined by Sir Isaac Newton in "Principia" (which is written in Latin), from Latin centri-, alternative combining form of centrum "center" (see center (n.)) + fugere "to flee" 

Centripetal tending or moving toward a centre," 1709, from Modern Latin, coined 1687 by Sir Isaac Newton, from Latin centri-, alternative combining form of centrum "centre"  + petere "to make for, go to; seek, strive after" (from PIE root *pet- "to rush, to fly"). Centripetal force is Newton's vim ... centripetam.

 

Early scientific ideas about centrifugal force were based upon intuitive perception, and circular motion was considered somehow more "natural" than straight-line motion. According to Domenico Bertoloni-Meli:

 

For Huygens and Newton centrifugal force was the result of a curvilinear motion of a body; hence it was located in nature, in the object of investigation. According to a more recent formulation of classical mechanics, centrifugal force depends on the choice of how phenomena can be conveniently represented. Hence it is not located in nature, but is the result of a choice by the observer. In the first case a mathematical formulation mirrors centrifugal force; in the second it creates it. 

 

It wasn't until the latter half of the 18th century that the modern "fictitious force" understanding of the centrifugal force as a pseudo-force artefact of rotating reference frames took shape. 

In a 1746 memoir by Daniel Bernoulli, "the idea that the centrifugal force is fictitious emerges unmistakably."

  • Like 1
Link to post
Share on other sites

Ever since long ago in pre-history, Mankind has observed that the Sun first becomes visible from one side of the observable horizon, and ceases to be visible on the opposite side of the observable horizon. Mankind called the first observation sunrise and the second sunset, terms we use and understand in our daily lives to this day. It is easy and useful to use and understand.

 

Among the ancient Greeks, several of the Pythagorean school believed in the rotation of Earth rather than the apparent diurnal rotation of the heavens. Perhaps the first was Philolaus (470–385 BCE), though his system was complicated, including a counter-earth rotating daily about a central fire. A more conventional picture was that supported by Hicetas, Heraclides and Ecphantus in the fourth century BCE who assumed that Earth rotated but did not suggest that Earth revolved about the Sun. In the third century BCE, Aristarchus of Samos suggested the Sun's central place.

 

However, Aristotle in the fourth century BCE criticized the ideas of Philolaus as being based on theory rather than observation. He established the idea of a sphere of fixed stars that rotated about Earth.This was accepted by most of those who came after, in particular Claudius Ptolemy (2nd century CE), who thought Earth would be devastated by gales if it rotated. In 499 CE, the Indian astronomer Aryabhata wrote that the spherical Earth rotates about its axis daily, and that the apparent movement of the stars is a relative motion caused by the rotation of Earth. He provided the following analogy: "Just as a man in a boat going in one direction sees the stationary things on the bank as moving in the opposite direction, in the same way to a man at Lanka (the name given in Hindu epics to the island fortress capital of the legendary Asura king Ravana in the epics of the Ramayana and the Mahabharata), the fixed stars appear to be going westward."

 

So, while it has been known for a very long time that the idea of the Sun moving across the sky, as it appears to do so from a point of observation on the ground, is wrong in the field of astronomy, it is a useful concept when applied to the activities of Mankind. In like manner, this concept of a force that acts away from the centre of a circular path of rotation has been shown to be false. However, it is an easier term to use than " the apparent result of the conservation of angular momentum". 

 

As for Semantics, centripetal and centrifugal  are words with distinct meanings and etymologies. The purpose of semantics is to propose exact meanings of words and phrases, and remove confusion. So if two words have distinct meanings, then each cannot be confused with the other. These two words have the additional advantage of having been invented by a known person, at a known time and having a definition published in the same document in which they were first used.

  • Like 1
Link to post
Share on other sites

Lets add another dimension to this pedanticism.

Where does the light go when it is switched off. We all know that we see things by seeing the reflected light from a surface. We cannot see light, unless we look at the source of the light.

So we sit in a room with walls made of mirrors which reflect the light. Turn the light off and it goes dark. Where has the light gone?

  • Like 1
Link to post
Share on other sites

IF centrifugal force doesn't happen how come multi stage water pumps are such high pressure and over revving flywheels fly apart in tension?

     That's a few days old. 

     Talking of turning off the lights, It's also turning me off. What is the purpose of all this dissection of  meaning?  Common usage generally dictates how and what language is used by the people at a certain time and is a dynamic thing ever being modified . Nev

  • Like 1
Link to post
Share on other sites

BUT

We Are losing the Australian English language at an alarming rate !.

Most modern conveniences are in a ' hieroglyphic ' language.

Most of which l don,t understand.

In the not too distant future we will be in the position, as we are now, with the Ancient English language.

NONECOMPREND 

spacesailor

Link to post
Share on other sites

It is fine to use the term centrifugal in common language as a short hand but not within science. I would argue that it is misleading.    If a child says asks "when the car travels around a corner why do you get pushed towards this side of the car?"  we could just say "centrifugal force" and leave it at that or we could give the scientifically correct answer and say that inertia causes you body  and the car to move in a straight line.  The car applies a turning force via its tyres on the road however our body wants to continue travelling in a straight line.  The car seat and perhaps the side of the car pushes us off off our straight course dictated by inertia.   

 

No one is saying that mud does not fly off a tyre.  It flies off the tyre due to inertial forces.  Rather than saying this is about pedantry we could say it is about accuracy. Like it or not centrifugal force is a  defined as a "fictitious" or "pseudo" force" in physics.   

 

Centrifugal Force

 

Julius Sumner Miller - Physics - Centrifugal Force pt. 1

 

 

 

Link to post
Share on other sites
15 minutes ago, octave said:

It is fine to use the term centrifugal in common language as a short hand but not within science

Fully agree

 

15 minutes ago, octave said:

The car applies a turning force via its tyres on the road however our body wants to continue travelling in a straight line. 

Fully agree

 

16 minutes ago, octave said:

The car seat and perhaps the side of the car pushes us off off our straight course dictated by inertia.   

Disagree. If the car is going in a straight line at a constant speed. our inertia will be equal to our mass times our velocity along that straight line. If the car turns, our inertia will keep us going in a straight line as the car underneath us changes direction. Eventually our straight path will intersect with a part of the car body and since we can't push the car body out, we stop and, united to the car body, we go around the corner.

 

26 minutes ago, octave said:

Rather than saying this is about pedantry we could say it is about accuracy.

Agree. Pedantry or semantics, I was aiming at scientific accuracy with all the stuff I have posted. I'm quite happy to call the feeling of being flung away from the centre of rotation of an object I am connected to centrifugal force when not involved in a discussion whose background is one of the Sciences.

 

3 hours ago, Yenn said:

Turn the light off and it goes dark. Where has the light gone?

When you pass an electric currant through a wire, one effect is to excite the atoms of the wire and they emit photons as the electrons move from a larger orbit radius to a smaller radius one. A photon is a wave and depending how many orbit jumps the electron makes, determines to frequency of the photon's wave. 

 

The speed of a photon is the product of its wavelength and frequency. The speed is always what we call the "speed of light", and is a constant value: 2.998 x 108 m/s. Therefore If we increase the wavelength, we decrease the frequency. 

Electromagnetic Spectrum | COSMOS

 

When we heat the wire, we produce photos of a wide variety of frequency/wavelength combinations. One set of combinations is the set that our eyes have evolved to react to - visible light. So the power goes on and the wire heats up. Photons of most of the combinations start leaving the wire and strike our eyes. Those in the visible light range, either coming directly from the wire, or reflected off surfaces, react with our eyes and we see things. At the same time, our eyes do not react to those photons whose frequency/wavelength combinations are outside the visible light range. We know those one are there because we have invented devices to detect them.

 

So, when the electric current stops moving through the wire, the electrons stop jumping from large orbits to small orbits and no more photons are emitted. No photons means no reaction in our eyes. If there is no reaction in our eyes, then we experience the blackness of blindness.  

 

You could argue that darkness, being the absence of the photons in the combination we call visible light, follows the last photon that is emitted from the wire. So it's not that darkness travels at the same speed as light, but it is the absence of light that travels at the same speed as light.

Link to post
Share on other sites
9 minutes ago, old man emu said:

Disagree. If the car is going in a straight line at a constant speed. our inertia will be equal to our mass times our velocity along that straight line. If the car turns, our inertia will keep us going in a straight line as the car underneath us changes direction. Eventually our straight path will intersect with a part of the car body and since we can't push the car body out, we stop and, united to the car body, we go around the corner.

 

That is precisely what I mean

Link to post
Share on other sites
4 hours ago, octave said:

The car seat and perhaps the side of the car pushes us off off our straight course dictated by inertia.   

 

3 hours ago, octave said:

That is precisely what I mean

I got thrown by the first part "the car seat". I was thinking of the contact surface between bum and seat cushion and seat back of a bench seat. I forgot about the sides of a bucket seat or one of those fancy Ricaro seats. Those sort of seats would certainly stop your movement along a tangent to the curve due to your inertia.

  • Agree 1
Link to post
Share on other sites

The question remains unanswered.

 

"Where does the light in a reflective cavity go, when it 'goes out'

 

Consider the fact that energy can never be destroyed.

 

Should all those photons, once created, just keep on bouncing around from one mirror to the next, for ever?

Edited by nomadpete
Link to post
Share on other sites

In a perfectly empty vacuum, a photon will go forever.

 

However I would put it to you that no mirror is going to perfectly reflect a photon without absorbing some of its energy, so it would not keep bouncing forever.  

Link to post
Share on other sites
4 minutes ago, nomadpete said:

Should all those photons, once created, just keep on bouncing around from one mirror to the next, for ever?

It's hard to talk about photons and their behaviour in layman's terms. When you try to stop a photon, like you would stop a massive particle, it vanishes … the energy goes to whatever you stopped it with.

 

The energy of a photon is given by

E={\frac  {hc}{\lambda }}
 

E=photon energy (electron volts)

h=Planck's constant (6.62607015×10−34 J⋅s) 

c= speed of electromagnetic waves (3 x 10^8 m/s)

λ  = wavelength

 

Since {\frac  {c}{\lambda }}=f, where f is frequency, the photon energy equation can be simplified to

E=hf

 

An FM radio station transmitting at 100 MHz emits photons with an energy of about 4.1357 × 10−7 eV. The photon energy at 1 Hz frequency is 6.62606957 × 10−34  so the energy of those FM station photons is 6.62606957 x 10−32  eV

 

The frequency of visible light is in the range of 400 to 790 x 10^12 Hz. The mid-range frequency we see as green. 

 

sRGB rendering of the spectrum of visible light
Color Wavelength Frequency Photon energy
Violet 380–450 nm 670–790 THz 2.75–3.26 eV
Blue 450–485 nm 620–670 THz 2.56–2.75 eV
Cyan 485–500 nm 600–620 THz 2.48–2.56 eV
Green 500–565 nm 530–600 THz 2.19–2.48 eV
Yellow 565–590 nm 510–530 THz 2.10–2.19 eV
Orange 590–625 nm 480–510 THz 1.98–2.10 eV
Red 625–700 nm 400–480 THz 1.65–1.98 eV

 

 

 

BUT HOW DID WE GET HERE FROM A STARTING POINT OF MASSES ON STRINGS GOING AROUND IN CIRCLES?

 

 

 

Link to post
Share on other sites

You should ask Yenn.
There is a connection.

When light acts like a particle, it's related to the energy of an electron going around a nucleus just like your ball but without utilising a string. I vaguely recall that light is emitted when an electron changes its orbit radius, obeying centrifugal force for a moment.

So, although a tangent is involved, Yenns question is related.

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...