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Natural Science Forum / Physics / Relativity / December 2006Relativists Conclusively Prove They Are a Bunch of Morons
I was recently asked to provide references to back up my claim that centrifugal force exists and has always existed in inertial frames. I have consistently argued that until recently, this was the norm throughout physics and engineering. I have been consistently ridiculed by the relativist lobby for doing so. Draper challenged me to produce evidence for my claim. I have a collection of old texts here and - guess what - the first three I looked at defined CENTRIFUGAL FORCE just as I have been doing so all along. See my latest post to PD for the details...or just get hold of any old text yourself.... The fact that the self deluded disciples of relativity will blatantly reject truth no matter how obvious it is, says a great deal about their whole theory. It is nothing but a weird exercise in self-hypnosis. I think it is time these people had a good look at themselves. Contributors like Geese, van de Mortuary, Wake, Piddlefuck, Hobba, Cardinale and 'Snipper' Tom Roberts <shrug> have conclusively demonstrated that they are totally indoctrinated by the false logic and impressive but meaningless terminology of the Einsteinian religion... like: curved space, geodesics, imaginary forces, spacetime, twins paradox, wormholes, RoS, mass increase, Minkowski, etc, etc,..... HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > I was recently asked to provide references to back up my claim that > centrifugal force exists and has always existed in inertial frames. I have > consistently argued that until recently, this was the norm throughout physics > and engineering. I have been consistently ridiculed by the relativist lobby for > doing so. Nobody is denying that the reaction force to the centripetal force always existed in inertial frames. So you are just arguing for a terminology change. You simply want to replace the words "reaction force to the centripetal force" with the words "centrifugal force". As was explained to you about 1000 times now, this terminology is particularly misleading because the word "centrifugal" has been reserved to describe a different force. The reason for this terminology shift (which occurred some time ago) was to clear up the confusion which you are still a victim of. This terminology shift had nothing to do with any "relativity". > Draper challenged me to produce evidence for my claim. > I have a collection of old texts here and - guess what - the first three I > looked at defined CENTRIFUGAL FORCE just as I have been doing so all along. > See my latest post to PD for the details...or just get hold of any old text > yourself.... Yes, yes, we all know about the old terminology. > The fact that the self deluded disciples of relativity will blatantly reject > truth Stop talking nonsense - truth of any kind cannot possibly depend on a naming convention. It's probably news to you but the real world doesn't change when one switches terminology used to describe it. > no matter how obvious it is, says a great deal about their whole theory. > It is nothing but a weird exercise in self-hypnosis. I think it is time these > people had a good look at themselves. I think it's time you stopped typing prose and looked at the actual physics and the actual equations. Everything else is at this point just an exercise in rhetoric. > Contributors like Geese, van de Mortuary, Wake, Piddlefuck, Hobba, Cardinale > and 'Snipper' Tom Roberts <shrug> have conclusively demonstrated that they are > totally indoctrinated by the false logic and impressive but meaningless > terminology of the Einsteinian religion... like: curved space, geodesics, > imaginary forces, spacetime, twins paradox, wormholes, RoS, mass increase, > Minkowski, etc, etc,..... You look like a fool now, you know that? You are arguing about a *name* as if the universe's very existence depended on it. You are introducing a bogus, strawman, entity - relativity - into the discussion which has nothing to do with this 100% Newtonian issue. This type of force is named "fictitious" not because of any "relativist agenda" but simply because it does not refer to any physical interaction between bodies, like other forces do. > HW. > www.users.bigpond.com/hewn/index.htm > > Thank christ there is one genuine physicist on the NG. To think an adult can be so infantile. Isn't there anything else in your life at all that you could be proud of? Something genuine for a change? -- Jan Bielawski >> I was recently asked to provide references to back up my claim that >> centrifugal force exists and has always existed in inertial frames. I have [quoted text clipped - 62 lines] >your life at all that you could be proud of? Something genuine for a >change? Be a man and admit you are wrong and I am right. Centrifugal forces have existed in inertial frames for hundreds of years.. HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > >> I was recently asked to provide references to back up my claim that > >> centrifugal force exists and has always existed in inertial frames. I have [quoted text clipped - 66 lines] > > Centrifugal forces have existed in inertial frames for hundreds of years.. In other words "la-la-la-I-can't-hear-you" and "I-am-right-because-I-say-so". And this comes from an adult. Pathetic. -- Jan Bielawski >> I was recently asked to provide references to back up my claim that >> centrifugal force exists and has always existed in inertial frames. I [quoted text clipped - 15 lines] > shift (which occurred some time ago) was to clear up the confusion > which you are still a victim of. As has been explained "a 1000 times", the word "centrifigal" had already been in place for centuries ("reserved") to mean the inverse of " centripetal" in Newtonian mechanics. The confusion (to which Henri is certainly not a victim) stems from the use of fictitious forces, centrifugal as well as centripetal. We have no need for fictitious forces, and in their condemnation some teachers want to ban the use of the word "centrifugal" altogether. > This terminology shift had nothing to do with any "relativity". He claimed that it does, but he didn't back it up; you claim that it does not, and similarly you didn't back it up. >> Draper challenged me to produce evidence for my claim. >> I have a collection of old texts here and - guess what - the first three [quoted text clipped - 6 lines] > > Yes, yes, we all know about the old terminology. If you had seen the reactions by some, you would know that either that is not true, or they were dishonest. >> The fact that the self deluded disciples of relativity will blatantly >> reject [quoted text clipped - 3 lines] > naming convention. It's probably news to you but the real world doesn't > change when one switches terminology used to describe it. Indeed. However, switching terminology can change the human world by confusing people. >> no matter how obvious it is, says a great deal about their whole theory. >> It is nothing but a weird exercise in self-hypnosis. I think it is time [quoted text clipped - 4 lines] > physics and the actual equations. Everything else is at this point just > an exercise in rhetoric. Also correct. >> Contributors like Geese, van de Mortuary, Wake, Piddlefuck, Hobba, >> Cardinale [quoted text clipped - 10 lines] > a bogus, strawman, entity - relativity - into the discussion which has > nothing to do with this 100% Newtonian issue. Quite to the contrary: in Newtonian mechanics there *are* no pseudoforces. The usual arguments in favour of the introduction of such forces are that it can be convenient and that it corresponds to the GRT approach. > This type of force is named "fictitious" not because of any "relativist > agenda" but simply because it does not refer to any physical > interaction between bodies, like other forces do. Right. Harald > Quite to the contrary: in Newtonian mechanics there *are* no pseudoforces. That's an incorrect statement. We live on a rotating frame of reference. It is convenient to do Newtonian mechanics on that frame of reference, for instance to model the flight of artillery shells. When doing so, pseudoforces must be taken into account. The people who fire big guns do not worry about general relativity, but they worry very much about modeling coriolis "force". - Randy | > Quite to the contrary: in Newtonian mechanics there *are* no pseudoforces. | [quoted text clipped - 7 lines] | relativity, but they worry very much about modeling coriolis | "force". So did the people who flew long range aircraft before GPS guidance. In the pseudo-theory of general relativity all forces are pseudo, flight paths are geodesic until the pseudo-jet stream takes them off course. >> Quite to the contrary: in Newtonian mechanics there *are* no >> pseudoforces. [quoted text clipped - 4 lines] > shells. When doing so, pseudoforces must be taken into > account. Sure that can be convenient, but please don't call that "Newtonian". "Pseudo-Newtonian" is OK. ;-) > The people who fire big guns do not worry about general > relativity, but they worry very much about modeling coriolis > "force". > > - Randy They can do just as well by just modeling Coriolis acceleration (which is a coordinate acceleration). No magical forces need to be invoked. Regards, Harald > >> Quite to the contrary: in Newtonian mechanics there *are* no > >> pseudoforces. [quoted text clipped - 7 lines] > Sure that can be convenient, but please don't call that "Newtonian". > "Pseudo-Newtonian" is OK. ;-) Well, it isn't relativistic. > > The people who fire big guns do not worry about general > > relativity, but they worry very much about modeling coriolis > > "force". > > They can do just as well by just modeling Coriolis acceleration (which is a > coordinate acceleration). No magical forces need to be invoked. Yes. I thought you were arguing that the only people who talked about frame-dependent acceleration terms were those doing GR. No judgement about "magic" is being made when one puts in centrifugal and coriolis acceleration terms. Yes, they are merely terms caused by the transformation between inertial and rotating coordinates, but all the artillery guy wants to know is that he has to include them. He's never likely to have to fire a shell in an inertial frame. - Randy >> >> Quite to the contrary: in Newtonian mechanics there *are* no >> >> pseudoforces. [quoted text clipped - 27 lines] >to know is that he has to include them. He's never likely >to have to fire a shell in an inertial frame. ...but if the calculations were carried out from the point of view of the inertial frame, they would be easier and the firing more accurate. > - Randy HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > >> >> Quite to the contrary: in Newtonian mechanics there *are* no > >> >> pseudoforces. [quoted text clipped - 30 lines] > ...but if the calculations were carried out from the point of view of the > inertial frame, they would be easier and the firing more accurate. No, they wouldn't be easier. The launch point is not a fixed point in the inertial earth-centered frame, and neither is the destination point. Each has a position that changes in time. Now you're trying to hit a moving target from a moving launch point. Much harder calculation. Some 19-year-old working out firing solutions while he himself is under fire does not really give a crap about how to describe the problem to an observer in space. And no, it wouldn't be more accurate. It's an equivalent calculation. Where would there be more or less accuracy? - Randy >> >> >> Quite to the contrary: in Newtonian mechanics there *are* no >> >> >> pseudoforces. [quoted text clipped - 43 lines] >And no, it wouldn't be more accurate. It's an equivalent >calculation. Where would there be more or less accuracy? I wont argue. > - Randy HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > I was recently asked to provide references to back up my claim that > centrifugal force exists and has always existed in inertial frames. Let us start with the definition of centrifugal force "centrifugal force - the apparent force that is felt by an object moving in a curved path that acts outwardly away from the center of rotation" This force exists in an inertial frame whenever you attempt to move a particle from straightline motion. > I have > consistently argued that until recently, this was the norm throughout > physics > and engineering. I have been consistently ridiculed by the relativist > lobby for > doing so. I sure hope that you don't take people on this newsgroup as being epresentative of the relativity community???? > Draper challenged me to produce evidence for my claim. I take it that he provided no source of definition of the term? To discuss any concept one must first define terms. > I have a collection of old texts here and - guess what - the first three I > looked at defined CENTRIFUGAL FORCE just as I have been doing so all > along. How have you been defining it? > See my latest post to PD for the details...or just get hold of any old > text [quoted text clipped - 4 lines] > truth no matter how obvious it is, says a great deal about their whole > theory. How many relativists have you met in real life, i.e. off this newsgroup? > It is nothing but a weird exercise in self-hypnosis. I think it is time > these [quoted text clipped - 8 lines] > imaginary forces, spacetime, twins paradox, wormholes, RoS, mass increase, > Minkowski, etc, etc,..... Terminology is never meaningless if it is well defined and each of the terms you mentioned are quite well defined. What does it mean to be well defined? It means that when you use the term in the presence of your peers and they understand exactly what you're referring to then that term is well defined *by definition*. Best wishes Pete >> I was recently asked to provide references to back up my claim that >> centrifugal force exists and has always existed in inertial frames. [quoted text clipped - 16 lines] >I sure hope that you don't take people on this newsgroup as being >epresentative of the relativity community???? Of course they are....typically religious fanatics. What is more, they never utter a scientific word between them. >> Draper challenged me to produce evidence for my claim. > [quoted text clipped - 6 lines] > >How have you been defining it? Just as the books say. In the case of two spinning objects connected by a spring, it is the outward force exerted by each object on the end of the spring. ....due to its directional change in momentum. >> See my latest post to PD for the details...or just get hold of any old >> text [quoted text clipped - 6 lines] > >How many relativists have you met in real life, i.e. off this newsgroup? I have met many genuine physicists who were obliged to cite Einsteiniana to pass exams but were forever suspicious of it..... >> It is nothing but a weird exercise in self-hypnosis. I think it is time >> these [quoted text clipped - 14 lines] >understand exactly what you're referring to then that term is well defined >*by definition*. The fact that an imaginary centrifugal force (actually there are two) exists in the rotating frame doesn't mean that NO centrifugal force exists in the inertial frame....unless one is indoctrinated with relativist type logic. So be a man and admit you are wrong and I am right. Centrifugal forces have existed in inertial frames for hundreds of years.. >Best wishes > >Pete HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > The fact that an imaginary centrifugal force (actually there are two) > exists in the rotating frame doesn't mean that NO centrifugal force exists > in the inertial frame....unless one is indoctrinated with relativist type > logic. I came on the tail-end of this, and not really sure what the argument is about so, perhaps, I'm speaking out of turn. It would seem logical to conclude the Earth and all the other objects that make up our solar system are subjected to centrifugal force as they orbit the sun since, if the sun disappeared, our system's objects would again conform to inertia and begin moving in straight paths... unless previously (or until) captured by larger objects. Planets are examples of inertial frames. Are you saying centrifugal force should play a part in any sort of movement of cosmic objects into a curved path (away from a straight path)? Inertia should apply regardless, one would think, and inertia is behind centrifugal force. Is that what you mean? Dictionary.com. The American Heritage® Science Dictionary. Houghton Mifflin Company. http://dictionary.reference.com/browse/centrifugal%20force centrifugal force An effect that seems to cause an object moving in a curve to be pushed away from the curve's center. Centrifugal force is not a true force but is actually the effect of inertia, in that the moving object's natural tendency is to move in a straight line. Dictionary.com. The American Heritage® Science Dictionary. Houghton Mifflin Company. http://dictionary.reference.com/search?q=centripetal%20force centripetal force A force acting on a moving body at an angle to the direction of motion, tending to make the body follow a circular or curved path. The force of gravity acting on a satellite in orbit is an example of a centripetal force; the friction of the tires of a car making a turn similarly provides centripetal force on the car. > HW. Be well - Pax > Let us start with the definition of centrifugal force > "centrifugal force - the apparent force that is felt by an object moving in > a curved path that acts outwardly away from the center of rotation" That is a VERY poor definition. So poor it is downright wrong. A human NEVER feels "centrifugal force". For instance, consider sitting in the right-hand seat of an automobile executing a sharp left turn. You will _feel_ the door on your right pushing you toward the center of the turn. You will feel no "outwardly" force at all, you'll just feel the door exerting an _inward_ force on you (plus a seat belt pushing the same way -- INWARD). An observer standing on the road will easily explain this -- your body wants to continue moving in a straight line, but the automobile is executing a left turn, and to keep you inside it the automobile must exert an INWARD force on your body. Go back to that old thread and its example of a fairgrounds with a carousel and hot dog stand. Please explain how the hot dog stand "feels" the "centrifugal force" applied to it by an observer on the carousel. Remember that this "centrifugal force" is millions of Newtons, which would be impossible to ignore if it were real or could actually be felt.... Tom Roberts >> Let us start with the definition of centrifugal force "centrifugal >> force - the apparent force that is felt by an object moving in a curved [quoted text clipped - 13 lines] > executing a left turn, and to keep you inside it the automobile must exert > an INWARD force on your body. You've never felt centrifugal force while riding in an auto? Everyone doesn't always wind up pushed up against the door. So, what you are saying is that we're really feeling the centripetal force, even if we don't come in contact with the door? Would the centripetal force be the result of our body-weight in that instance? However, aren't you side-stepping into the realm of semantics? It is the result of inertia trying to keep us going straight that causes us to feel the effects of centripetal force in the first place... cause and effect... inertia first as cause, centripetal force second as effect. If inertia was not being battled, we would feel no force, so centrifugal force is valid. The force we feel is directly related to the amount of inertia we have built-up, not the centripetal force which, in most cases, remains constant. When driving a car, you can only step on the breaks so hard and turn the wheel so far, but the velocity of the vehicle can vary markedly, and the inertia imparted due to the velocity of the car determines the final results, when the exact same centripetal forces are applied. What you're saying is equivalent to giving the reason a car crumples when it hits a brick wall as being due to the force exerted by the brick wall. The energy from our inertial motion in a given, straight-line direction becomes centrifugal force when our course is diverted, and that is what gives the centripetal force its strength. The faster our initial straight-line velocity, the greater the response to centripetal force when our original (inertial) course is diverted. What we feel is the force of inertial energy being diverted, and that energy is centrifugal. > Tom Roberts Be well - Pax >>> Let us start with the definition of centrifugal force "centrifugal >>> force - the apparent force that is felt by an object moving in a curved [quoted text clipped - 19 lines] >contact with the door? Would the centripetal force be the result of our >body-weight in that instance? Tom is basically right on this one. You feel the centripetal force pushing you INWARD rather than the CENTRIFUGAL force your body exerts on the wall....even though they are both the same magnitude. However this may depend on the setup.... Also, your body is not infinitesimally thin and there will be a pressure gradient across it because of the 'mw^2r' bizzo. I'm sure that gradient will be felt in most cases. That's another story.. >However, aren't you side-stepping into the realm of semantics? It is the >result of inertia trying to keep us going straight that causes us to feel >the effects of centripetal force in the first place... cause and effect... >inertia first as cause, centripetal force second as effect. If inertia was >not being battled, we would feel no force, so centrifugal force is valid. Of course it's valid...and has been so for hundreds of years. Tom and his disciples prefer to call is a 'reaction to centripetal force'...which is ridiculous. Note: if an object is suddenly pulled linearly by for instance a rope, the force THE OBJECT EXERTS ON THE ROPE can rightly be regarded as a 'reaction' to the applied force. This is not true in the rotating system as I have tried to get across to these people. Both centripetal and centrifugal forces must originate and exist together, as a pair. (in the inertial frame) The latter cannot be regarded as a 'reaction to the former' because the former depends on the latter for its very existence. >The force we feel is directly related to the amount of inertia we have >built-up, not the centripetal force which, in most cases, remains constant. The most prominent force you feel is the centripetal one...although you are also well aware that you are simultaneously 'pushing' on the wall. If you are swinging around on a rope, you certainly know your body is pulling on the rope. Consider what happens if you are standing on the floor of a rotating cylinder with a rope around your waist. You can't see outside. You are in the rotating frame. You feel the rope pulling your waist towards its other end... but you aren't moving wrt the floor in that direction. You also feel an invisible force pushing your head and legs AWAY FROM the rope. You end up bent over like this: |---------c ........probably with spinal damage..... Now consider if you are leaning up against the cylinder wall. The question is, "do you feel the wall pushing you inward...or do you feel yourself pushing the wall outward". You certainly aren't moving inwards across the floor...but you don't have to push outwards on the floor to prevent that movement. You have to manufacture an outward (or 'fictitious centrifugal') force to explain why you aren't moving. Here's another interesting exercise. (use fixed pitch fonts) ______________________________| M1-\/\/\/\/\/\/\/\/\/\/\/-------|M2 Two extremely large masses are separated by both a rigid rod and an extended spring. If the rod is suddenly removed, what forces keep the spring extended? >When driving a car, you can only step on the breaks so hard and turn the >wheel so far, but the velocity of the vehicle can vary markedly, and the >inertia imparted due to the velocity of the car determines the final >results, when the exact same centripetal forces are applied. In the inertial frame, the car exerts a CENTRIFUGAL FORCE on the road as it turns. >What you're saying is equivalent to giving the reason a car crumples when it >hits a brick wall as being due to the force exerted by the brick wall. In the car frame, that is true. The driver sees the wall moving towards him. The wall's momentum decrease crushes the car. >The >energy from our inertial motion in a given, straight-line direction becomes [quoted text clipped - 3 lines] >(inertial) course is diverted. What we feel is the force of inertial energy >being diverted, and that energy is centrifugal. Whenever an object moves in a circle, another object does the same, lagging 180 behind. This fact is fundamental to the understanding of centrifugal forces. >> Tom Roberts > >Be well - Pax HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. >>>> Let us start with the definition of centrifugal force "centrifugal >>>> force - the apparent force that is felt by an object moving in a curved [quoted text clipped - 28 lines] > gradient across it because of the 'mw^2r' bizzo. I'm sure that gradient > will be felt in most cases. That's another story.. Just answer me this: Is the amount of centripetal force you feel due to your inertia? >> However, aren't you side-stepping into the realm of semantics? It is the >> result of inertia trying to keep us going straight that causes us to feel [quoted text clipped - 4 lines] > > Of course it's valid...and has been so for hundreds of years. More like almost as long as the universe has been around. <grin> Man didn't invent it, he just recognized it. > Tom and his disciples prefer to call is a 'reaction to centripetal > force'...which is ridiculous. Semantically (relativistically?), guess it is. > Note: if an object is suddenly pulled linearly by for instance a rope, the > force THE OBJECT EXERTS ON THE ROPE can rightly be regarded as a [quoted text clipped - 5 lines] > The latter cannot be regarded as a 'reaction to the former' because the > former depends on the latter for its very existence. That's very true, and I completely agree. However, the amount of force exerted on the object undergoing change of direction definitely depends on the initial inertia of that object. Though there's energy in the centripetal force too. >> The force we feel is directly related to the amount of inertia we have >> built-up, not the centripetal force which, in most cases, remains [quoted text clipped - 4 lines] > you are swinging around on a rope, you certainly know your body is pulling > on the rope. Yes. The kid's game Pop-The-Whip comes to mind. (No wall pushing though.) No, we don't feel inertial force until some other force acts upon us trying to counter it by changing our direction, however, by the same token, we wouldn't feel the altering force if we weren't under the influence of inertia. The force we feel when our direction is changed is due to two opposing forces coming into conflict: the inertial force and the force countering it. > Consider what happens if you are standing on the floor of a rotating > cylinder with a rope around your waist. You can't see outside. You are in [quoted text clipped - 11 lines] > manufacture an outward (or 'fictitious centrifugal') force to explain why > you aren't moving. Inertia isn't fictitious, so I guess what must be fictitious is the effect of the two forces when combined. If the rotation of the cylinder was sufficient, I would feel a force similar to gravity. If the force was greater than that of the gravity pulling down toward my feet, I would have the illusion I was lying flat within a cylinder lying at a slight angle on its side. I would consider the g-force to be pressing down on me, rather than the wall pushing up on me... which is exactly how I felt when I was a kid in an amusement park centrifuge. My mind would tell me the wall was stationary and couldn't push on me, therefore the force was to the front of me pushing down. So perhaps that's why I'm having a problem with this whole thing. :) Guess it's a matter of perception... but isn't everything? When riding in a car, if I'm pressed into the door during a turn, I feel the force throughout my body, originating from the side away from the door. The door stops my outward movement, but I don't have the sensation it's pushing in on me, because I know it isn't. The door is rigid, fixed in place, I'm the one who's moving. When I was young, we had a horse who had a peculiar habit. When we turned him toward the barn, nothing could stop him from running full-out, then making an almost 90 degree turn at the corner of the barn, still at a full gallop. Riding bareback was a feat on that horse. If you weren't holding on for dear life, when he made that 90 degree turn you kept going straight and landed hard in the dirt, because he centripetaled while you kept on inertialing. <grin> Even when you made the turn and stayed on him, you definitely felt your inertia trying to yank you from his back. > Here's another interesting exercise. (use fixed pitch fonts) > ______________________________| [quoted text clipped - 3 lines] > extended spring. If the rod is suddenly removed, what forces keep the > spring extended? If the spring is attached to both the masses, then the inertia of the two extremely large masses. "A body at rest tends to stay at rest, a body in motion tends to stay in motion." The force of the spring would have to overcome the inertia of at least one of the objects before it could contract. >> When driving a car, you can only step on the breaks so hard and turn the >> wheel so far, but the velocity of the vehicle can vary markedly, and the [quoted text clipped - 3 lines] > In the inertial frame, the car exerts a CENTRIFUGAL FORCE on the road as > it turns. Centripetal. The centrifugal force is the inertia of the car attempting to counter the tires turning it. Dictionary.com. The American Heritage® Science Dictionary. Houghton Mifflin Company. http://dictionary.reference.com/browse/centripetal%20force centripetal force "A force acting on a moving body at an angle to the direction of motion, tending to make the body follow a circular or curved path. The force of gravity acting on a satellite in orbit is an example of a centripetal force; the friction of the tires of a car making a turn similarly provides centripetal force on the car." >> What you're saying is equivalent to giving the reason a car crumples when >> it hits a brick wall as being due to the force exerted by the brick wall. > > In the car frame, that is true. The driver sees the wall moving towards > him. The wall's momentum decrease crushes the car. Very relativistic. If the car was moving at 100 mph, it would be history, if it was moving at 2mph, it would bump lightly. The force of the impact is directly related to the inertia of the car. In both instances, the wall is just standing there being a wall. They say, it's not the fall that kills you, it's the sudden stop. But it's not the ground that's the culprit in your demise, it's the inertia imparted by the force of gravity. At 1/100th the gravity, the ground wouldn't hurt you. >>The energy from our inertial motion in a given, straight-line direction >>becomes centrifugal force when our course is diverted, and that is what [quoted text clipped - 6 lines] > lagging 180 behind. This fact is fundamental to the understanding of > centrifugal forces. Remember being tied by a rope to a pole in the middle of a rotating cylinder? The wall doesn't move, the floor doesn't move, and the pole doesn't move. Only you move. So guess I really don't catch what you mean. Could you rephrase? > HW. Be well - Pax "Pax" <SherriFWhite@sbcglobal.net> wrote in message news:Hswhh.7486 > Just answer me this: Is the amount of centripetal force you feel due to > your inertia? To understand the answer consider first what an inertial force is, since the centrifugal force is one of them. An inertial force, by definition, is that force (time rate of change of momentum) which exists in non-inertial frames of reference and is due to the change of reference frame. The centrifugal force is that force which is observed by an observer who is at rest in a rotating frame. In a carousel you are at rest in the rotating frame. If you jump up in the air then you will accelerate towards the rim of the carousel. If you then stand up against one of the horses then it will exert a force on you just as the floor exerts a force on you. Since you are now at rest there is another force acting on you, the horse-force. :) Since you are at rest in this frame the total force must be zero. The centrifugal force is directed outward, away from the center of rotation (this is the force actually felt by the observer at rest, so I have no idea what Tom was referring to) and the horse-force is exerted on you and acts toward the center of rotation. The sum of these two forces is zero. However the centrifugal force is there whether there is an external force is acting or not. Actually I don't care for my definition. It really doesn't capture what an inertial force is. For several quotes from the literature on inertial forces please see http://www.geocities.com/physics_world/gr/inertial_force.htm Pete > "Pax" <SherriFWhite@sbcglobal.net> wrote in message news:Hswhh.7486 > [quoted text clipped - 7 lines] > centrifugal force is that force which is observed by an observer who is at > rest in a rotating frame. Even inertial FoRs have inertia, hence the name. :) All "inertial frame" means is a frame that is in constant motion, neither accelerating nor decelerating. While we're sitting at our computers typing, we're in an inertial frame with an acceleration toward the center of the Earth equal to 1G, experiencing a planetary rotational speed of approx. 1,000 mph (depending on your location), as the Earth orbits the sun at approx. 67,000 mph... but we consider ourselves to be "at rest". Dictionary.com. The American Heritage® Science Dictionary. Houghton Mifflin Company. http://dictionary.reference.com/browse/Newton's%20laws%20of%20motion Newton's laws of motion [Open Quote] The three laws proposed by Sir Isaac Newton concerning relations between force, motion, acceleration, mass, and inertia. These laws form the basis of classical mechanics and were elemental in solidifying the concepts of force, mass, and inertia. o Newton's first law states that a body at rest will remain at rest, and a body in motion will remain in motion with a constant velocity, unless acted upon by a force. This law is also called the law of inertia. o Newton's second law states that a force acting on a body is equal to the acceleration of that body times its mass. Expressed mathematically, F = ma, where F is the force in Newtons, m is the mass of the body in kilograms, and a is the acceleration in meters per second per second. o Newton's third law states that for every action there is an equal and opposite reaction. Thus, if one body exerts a force F on a second body, the first body also undergoes a force of the same strength but in the opposite direction. [Close Quote] > In a carousel you are at rest in the rotating frame. If you jump up in the > air then you will accelerate towards the rim of the carousel. If you then [quoted text clipped - 14 lines] > > http://www.geocities.com/physics_world/gr/inertial_force.htm How about this? Centrifugal force From Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Centrifugal_force [Open Quote] Centrifugal force (from Latin centrum "center" and fugere "to flee") is a term which may refer to two different forces which are related to rotation. Both of them are oriented away from the axis of rotation, but the object on which they are exerted differs. 1) A real or "reactive" centrifugal force occurs in reaction to a centripetal acceleration acting on a mass. This centrifugal force is equal in magnitude to the centripetal force, directed away from the center of rotation, and is exerted by the rotating object upon the object which imposes the centripetal acceleration. Although this sense was used by Isaac Newton, it is only occasionally used in modern discussions. 2) A pseudo or "fictitious" centrifugal force appears when a rotating reference frame is used for analysis. The (true) frame acceleration is substituted by a (fictitious) centrifugal force that is exerted on all objects, and directed away from the axis of rotation. Both of the above can be easily observed in action for a passenger riding in a car. If a car swerves around a corner, a passenger's body seems to move towards the outer edge of the car and then pushes against the door. In the reference frame that is rotating together with the car (a model which those inside the car will often find natural), it looks like a force is pushing the passenger away from the center of the bend. This is a fictitious force, not an actual force exerted by some other object. The illusion occurs when the reference frame is the car, because that ignores the car's acceleration. A number of physicists treat it much as if it were a real force, as they find that it makes calculations simpler and gives correct results. However, the force with which the passenger pushes against the door is very real. That force is called a reaction force because it results from passive interaction with the car which actively pushes against the body. As it is directed outward, it is a centrifugal force. Note that this real centrifugal force does not appear until the person touches the body of the car. The car also exerts an equal but opposite force on the person, called "centripetal force". In this case the centrifugal force is canceled by the centripetal force, and the net force is zero, thus the person does not accelerate with respect to the car. [Close Quote] Notice this statement: "This is a fictitious force, not an actual force exerted by some other object. The illusion occurs when the reference frame is the car, because that *ignores the car's acceleration*." > Pete Be well - Pax >> "Pax" <SherriFWhite@sbcglobal.net> wrote in message news:Hswhh.7486 >> [quoted text clipped - 9 lines] > > Even inertial FoRs have inertia, hence the name. :) Frames of reference don't have inertia, whether inertial or non-inertial. >> Actually I don't care for my definition. It really doesn't capture what >> an inertial force is. For several quotes from the literature on inertial [quoted text clipped - 20 lines] > imposes the centripetal acceleration. Although this sense was used by > Isaac Newton, it is only occasionally used in modern discussions. Sounds oaky. > 2) A pseudo or "fictitious" centrifugal force appears when a rotating > reference frame is used for analysis. The (true) frame acceleration is > substituted by a (fictitious) centrifugal force that is exerted on all > objects, and directed away from the axis of rotation. The terms "pseudo" and "fictitious" have no meaning for me. I disaprove their use when describing inertial forces. Regards Pete > The terms "pseudo" and "fictitious" have no meaning for me. I disaprove > their use when describing inertial forces. OK, as far as it goes. But in an elementary discussion how do you describe the "centrifugal force" on the hot dog stand when observed from the rotating carousel? -- it is a figment of the observer's imagination, and "fictitious" seems like a reasonable description of that. I am not alone in this, and indeed much of the physics community uses that word in this context. Tom Roberts >> The terms "pseudo" and "fictitious" have no meaning for me. I disaprove >> their use when describing inertial forces. [quoted text clipped - 5 lines] >alone in this, and indeed much of the physics community uses that word >in this context. ...and rightly so..... But that does not mean other centrifugal forces don't exist in inertial frames. Just look up any old physics text Tom. I have already given three references. >Tom Roberts HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > >> The terms "pseudo" and "fictitious" have no meaning for me. I disaprove > >> their use when describing inertial forces. [quoted text clipped - 9 lines] > > But that does not mean other centrifugal forces don't exist in inertial frames. The only issue that remains is just terminological then. It's not worth discussing, it's just a name. Point being that one of these forces is of different nature than the others and that modern usage reserves the word "centrifugal" to that force rather than applying it generically. -- Jan Bielawski >> >> The terms "pseudo" and "fictitious" have no meaning for me. I disaprove >> >> their use when describing inertial forces. [quoted text clipped - 14 lines] >of different nature than the others and that modern usage reserves the >word "centrifugal" to that force rather than applying it generically. here you go again....'modern teminology'.... Only brainwashed relativists have ever heard of this 'modern terminology.... HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > >> >> The terms "pseudo" and "fictitious" have no meaning for me. I disaprove > >> >> their use when describing inertial forces. [quoted text clipped - 16 lines] > > here you go again....'modern teminology'.... What's wrong with saying "modern terminology"? > Only brainwashed relativists have ever heard of this 'modern terminology.... As opposed to non-brainwashed relativists? You keep dragging relativity into it - isn't it Newtonian mechanics that we are discussing? Current standard terminological convention is to use the word "centrifugal" only in a precise technical context rather than in a generic one as in the past. Why is this silly terminological shift such a big deal for you? -- Jan Bielawski >> >> >> The terms "pseudo" and "fictitious" have no meaning for me. I disaprove >> >> >> their use when describing inertial forces. [quoted text clipped - 23 lines] >As opposed to non-brainwashed relativists? You keep dragging relativity >into it - isn't it Newtonian mechanics that we are discussing? It is..but for some unknown reason, the relativist lobby has made it a political issue. >Current standard terminological convention is to use the word >"centrifugal" only in a precise technical context rather than in a >generic one as in the past. Crap. >Why is this silly terminological shift such >a big deal for you? It isn't. It is a big deal for the relativists. Their religion is under threat. Apparently GR requires that centrifugal force does not exist in inertial frames. Why I don't know... HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > [...] > >What's wrong with saying "modern terminology"? > > > >> Only brainwashed relativists have ever heard of this 'modern terminology.... Nonsense. Whatever. > >As opposed to non-brainwashed relativists? You keep dragging relativity > >into it - isn't it Newtonian mechanics that we are discussing? > > It is..but for some unknown reason, the relativist lobby has made it a > political issue. What "relativist lobby"? Nobody ever heard of such thing. > >Current standard terminological convention is to use the word > >"centrifugal" only in a precise technical context rather than in a > >generic one as in the past. > > Crap. It's a fact that this is current practice. > >Why is this silly terminological shift such > >a big deal for you? > > It isn't. It is a big deal for the relativists. No, what an idea! > Their religion is under threat. It's just a theory in physics. Where you and all the other cranks around here get this idiotic concept of science as "religion" which for some incomprehensible reason must "defend" relativity come hell or high water I'll never know. (Of course real-life physicists (not the phantoms imagined on this NG) would get very excited if relativity was disproved. Far from being thrown out as a "heretic", anyone showing experimentally, say, the failure of the Lorentz invariance would almost certainly be rewarded with a Nobel. Unfortunately, such pedestrian scenario is far too threatening to cranks because in their opinion it makes them look inadequate, so they feel compelled to construct labyrinthine conspiracies which demean the "establishment".) > Apparently GR requires that centrifugal force does not exist in inertial > frames. > Why I don't know... What does GR have to do with it? Are you on some medication or something? -- Jan Bielawski > > [...] > > >What's wrong with saying "modern terminology"? [quoted text clipped - 32 lines] > some incomprehensible reason must "defend" relativity come hell or high > water I'll never know. It's because they haven't been able to talk us out of it yet. They find what they think is a flaw in the theory. They work with it and develop it. They take it to this newsgroup hoping to get an amazing following, believing that they will be acclaimed as better than Einstein. The newsgroup takes the theory apart at the first misconception, which in all likelihood is something trivial that they've seen a hundred times before. (Some of them can be quite subtle, however). So, of course, absolutely nothing happens in the world of physics. The odds of some random, half-educated layman taking apart relativity (or extending it, for that matter) at this late date is minuscule. The poster thinks "I can't have been wrong. It's so simple, what I've done. Why are they sticking to their theory? It's almost religious..." They're wrong, of course. We rejected their theory or disproof because they didn't understand the theory properly in the first place and haven't actually improved or debunked relativity. We don't take what Einstein (or, for that matter, Newton) did religiously, because we know they made all sorts of mistakes. But they were astoundingly right on some important things, and we keep those and don't give *those bits* up without real evidence. > (Of course real-life physicists (not the phantoms imagined on this NG) > would get very excited if relativity was disproved. Far from being [quoted text clipped - 14 lines] > -- > Jan Bielawski JanPB says... >> Apparently GR requires that centrifugal force does not exist in inertial >> frames. >> Why I don't know... > >What does GR have to do with it? GR doesn't have anything to do with it, of course, but the nature of "fictitious forces" is clearest in 4-D pseudo-Riemannian geometry: All fictitious forces are accounted for by the single expression, occurring in the equations of motion for a test particle: Gamma^u_vw V^v V^w This single expression includes centrifugal force, Coriolis forces, "g-forces" due to linear acceleration. -- Daryl McCullough Ithaca, NY >> Why is this silly terminological shift such a big deal for you? > [quoted text clipped - 3 lines] > > Why I don't know... ROFL!!! > HW. Be well - Pax > As opposed to non-brainwashed relativists? You keep dragging relativity > into it - isn't it Newtonian mechanics that we are discussing? Newtonian mechanics didn't set up real-world incompatibles then try to justify some valid association between them through the use of fiction. The only way any of what you're talking about could be applicable is in the case of Relativity, not Newtonian mechanincs... except as they correspond to Relativity. > Current standard terminological convention is to use the word > "centrifugal" only in a precise technical context rather than in a generic > one as in the past. Why is this silly terminological shift such a big deal > for you? Because it completely ignores reality? Centrifugal force, as it is classically defined... and experienced in everyday life too, by the way... is a real force, not an imaginary one. In a rotating space colony (such as the once-proposed L5 Colony), where the rotation imparts artificial gravity to the occupants within, who would be living on the interior surface of the cylinder's wall, the consideration of the real centrifugal force pushing outward on the cylinder's wall is responsible for determining the required over-all strength of construction of the cylinder. The inertial weight (probably 1g) imparted to the living quarters, soil, people... in short, everything placed on the inside wall of the cylinder... must be considered. Why? Because, due to the rotation of the cylinder, everything of mass in contact with the outer wall pushes *out* on that wall in a very real way. > Jan Bielawski Be well - Pax > Centrifugal force, as it is > classically defined... and experienced in everyday life too, by the way... > is a real force, not an imaginary one. You are wrong. How does that hot dog stand "experience" the mega-Newton "centrifugal force" on it that the carousel rider assigns to it? You are confusing "centrifugal force" with the real centripetal force -- that is what you feel and "experience". > In a rotating space colony (such as the once-proposed L5 Colony), where the > rotation imparts artificial gravity to the occupants within, who would be > living on the interior surface of the cylinder's wall, the consideration of > the real centrifugal force pushing outward on the cylinder's wall There is no such force. The wall pushes INWARD on the people, who would otherwise move in a straight line (tangential to the wall because of their motion relative to the center of the colony). The key point is to analyze the situation in an INERTIAL frame. Then objects with no net force move in straight lines. In the inertial frame of the center of the colony it is easy to see that without the walls pushing INWARD the people would move outward in straight lines tangential to the walls where each person is located. Note the people would not move radially outward, because they have an initial velocity tangential to the wall where they are located. Tom Roberts > > Centrifugal force, as it is > > classically defined... and experienced in everyday life too, by the way... [quoted text clipped - 5 lines] > You are confusing "centrifugal force" with the real centripetal force -- > that is what you feel and "experience". We don't "feel" (experience"?) any force unless it is non-uniform i.e. is not applied equally throughout our bodies > > In a rotating space colony (such as the once-proposed L5 Colony), where the > > rotation imparts artificial gravity to the occupants within, who would be [quoted text clipped - 4 lines] > otherwise move in a straight line (tangential to the wall because of > their motion relative to the center of the colony). What's the name of the force that "pushes INWARD?" > The key point is to analyze the situation in an INERTIAL frame. Then > objects with no net force move in straight lines. In the inertial frame [quoted text clipped - 3 lines] > would not move radially outward, because they have an initial velocity > tangential to the wall where they are located. In the INERTIAL frame, what's the name of the force that is causing these people to move in circles? Barry > > There is no such force. The wall pushes INWARD on the people, who would > > otherwise move in a straight line (tangential to the wall because of > > their motion relative to the center of the colony). > >What's the name of the force that "pushes INWARD?" It is a contact force, sometimes called a "normal" force due to the direction of the force with regard to the plane of the surface. In the case of circular motion, there is another descriptor of the force that again refers to its direction: centripetal. But the essential nature of the force is the electrostatic repulsion that keeps the atoms of one material from penetrating the atoms of another material. PD > We don't "feel" (experience"?) any force unless it is non-uniform i.e. > is not applied equally throughout our bodies Right. Our pressure-sensing nerves are differential sensors that respond to strain (mechanical strain, not physiological strain). So we cannot feel "centrifugal force", "Coriolis force", or "gravitational force", because each of them is proportional to the mass of the object, and cannot induce any strain. The real commonality here is that all three of these "forces" disappear in appropriate coordinates (inertial ones for the first two, freely falling ones for the third; in GR these are the same). >>> In a rotating space colony [...] >> The wall pushes INWARD on the people, > What's the name of the force that "pushes INWARD?" Generically this is a centripetal force. In this instance it is a force of contact (ultimately of electromagnetic origin as the atoms in the wall push on the atoms of the people). > In the INERTIAL frame, what's the name of the force that is causing > these people to move in circles? Generically this is a centripetal force. In this instance it is a force of contact (ultimately of electromagnetic origin as the atoms in the wall push on the atoms of the people). This is a real force, and is independent of coordinates (unlike the three "forces" mentioned above in quotes). Tom Roberts > > We don't "feel" (experience"?) any force unless it is non-uniform i.e. > > is not applied equally throughout our bodies [quoted text clipped - 3 lines] > because each of them is proportional to the mass of the object, and > cannot induce any strain. Actually, I think we can as long as there is a sufficient differential in the so-called force across the dimension of the body. One can feel a centrifugal force on a playground carousel if it is spinning fast enough, just as one can feel a gravitational force if it varies strongly enough -- these are called tidal effects. PD > The real commonality here is that all three of these "forces" disappear > in appropriate coordinates (inertial ones for the first two, freely [quoted text clipped - 15 lines] > > Tom Roberts >> > We don't "feel" (experience"?) any force unless it is non-uniform i.e. >> > is not applied equally throughout our bodies [quoted text clipped - 9 lines] > enough, just as one can feel a gravitational force if it varies > strongly enough -- these are called tidal effects. There are no tidal effects in a rotating frame in flat spacetime.How do you justify the existance of these tidal effects? Regards Pete > > > We don't "feel" (experience"?) any force unless it is non-uniform i.e. > > > is not applied equally throughout our bodies [quoted text clipped - 9 lines] > enough, just as one can feel a gravitational force if it varies > strongly enough -- these are called tidal effects. Crank Alert > PD > [quoted text clipped - 17 lines] > > > > Tom Roberts >> Our pressure-sensing nerves are differential sensors that respond >> to strain (mechanical strain, not physiological strain). So we cannot [quoted text clipped - 7 lines] > enough, just as one can feel a gravitational force if it varies > strongly enough -- these are called tidal effects. Not likely. Those nerves measure strain on a scale of a millimeter or less. It is _certainly_ impossible for a human to experience a gravitational force that varies significantly over such a distance. And for a rotation to vary on that scale would probably require far too much acceleration for the human to survive. It is not the "centrifugal force" one feels, it is the centripetal force, and its effects on both pressure-sensing nerves and the semicircular canals o the inner ear. The "centrifugal force" is merely an artificial bookkeeping device used by an observer in rotating coordinates. Tom Roberts > > We don't "feel" (experience"?) any force unless it is non-uniform i.e. > > is not applied equally throughout our bodies [quoted text clipped - 4 lines] > because each of them is proportional to the mass of the object, and > cannot induce any strain. Subject to your corrections (which would be MUCH appreciated!), the way an engineering friend explained it to me, the word "force" is seriously abused in common speech. If you stretch a spring between your hands while otherwise holding it steady, no forces at all are operative on the spring! Force necessarily implies acceleration via the classical F=ma, and the spring is not accelerating. Instead, the spring is under "tension", a fundamentally different concept. Force is a vector, while tension is a tensor. Unfortunately, force and tension use the same units, Newtons, resulting in much confusion. As you point out, we cannot feel force. Forces accelerate masses, and the accelerating masses do not experience any strain. On the other hand, we do feel tensions. Tensions do not accelerate, but they do induce strain. Jerry >> > We don't "feel" (experience"?) any force unless it is non-uniform i.e. >> > is not applied equally throughout our bodies [quoted text clipped - 4 lines] >> because each of them is proportional to the mass of the object, and >> cannot induce any strain. Gord, look who's back... >Subject to your corrections (which would be MUCH appreciated!), the >way an engineering friend explained it to me, the word "force" is >seriously abused in common speech. If you stretch a spring between >your hands while otherwise holding it steady, no forces at all are >operative on the spring! I'm afraid Minor Crank has advised you wrongly yet again Jerry. If a string is extended, there must be an outward force acting on each of its ends. >Force necessarily implies acceleration via >the classical F=ma, and the spring is not accelerating. Acceleration occurs only if the sum of all forces is zero....as it is in the above case...You are pulling the spring outward. The stretched molecular bonds of the spring are pulling back on you. Every force is balanced by an equal and opposite one.. The result..no acceleration. >Instead, the >spring is under "tension", a fundamentally different concept. Force >is a vector, while tension is a tensor. What a load of crap...there is no need for any tensor. You're talking about a linear tension...just a stretching of molecular bonds away from their equilibrium positions...they want to return there...so they pull on your hands. >Unfortunately, force and >tension use the same units, Newtons, resulting in much confusion. The has been absolutely NO confusion here. the only one confused is YOU. >As you point out, we cannot feel force. Load of crap... a force will give rise to a pressure change across our bodies...which we can easily detect. >Forces accelerate masses, and >the accelerating masses do not experience any strain. They do if the force is applied to one side. You are confusing this situation with free fall under gravity. >On the other hand, we do feel tensions. Tensions do not accelerate, >but they do induce strain. This would be one of the worst posts I have seen here, Jerry. You would be better off not consulting Crank at all. >Jerry HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. > >> > We don't "feel" (experience"?) any force unless it is non-uniform i.e. > >> > is not applied equally throughout our bodies [quoted text clipped - 6 lines] > > Gord, look who's back... Only for the Christmas break. Medical school is way too much work for me to be wasting time here with the likes of you. I'm interested in what Tom has to say. > >Subject to your corrections (which would be MUCH appreciated!), the > >way an engineering friend explained it to me, the word "force" is [quoted text clipped - 3 lines] > > I'm afraid Minor Crank has advised you wrongly yet again Jerry. If I meant my brother, I would have SAID my brother, not an "engineering friend". > If a string is extended, there must be an outward force acting on each of its > ends. [quoted text clipped - 6 lines] > opposite one.. > The result..no acceleration. This is the confusion which Roger said was inevitable. Anyhow, I'm here to see what Tom has to say, not you. Bye, Jerry >> >> > We don't "feel" (experience"?) any force unless it is non-uniform i.e. >> >> > is not applied equally throughout our bodies [quoted text clipped - 36 lines] > >Anyhow, I'm here to see what Tom has to say, not you. I can tell you what Snipper has to say....lots of big meaningless words. >Bye, >Jerry HW. www.users.bigpond.com/hewn/index.htm Thank christ there is one genuine physicist on the NG. | >> >> > We don't "feel" (experience"?) any force unless it is non-uniform i.e. | >> >> > is not applied equally throughout our bodies [quoted text clipped - 39 lines] | I can tell you what Snipper has to say....lots of big meaningless words. | Aww, ain't love sweet? >> Centrifugal force, as it is classically defined... and experienced in >> everyday life too, by the way... is a real force, not an imaginary one. > > You are wrong. No I'm not, in the context of everyday experience. Inertia is very real. > How does that hot dog stand "experience" the mega-Newton "centrifugal > force" on it that the carousel rider assigns to it? It doesn't, because what you're talking about with the hot dog stand is not the same thing as real centrifugal force, a name commonly understood to mean the force felt as a result of diverted momentum. It doesn't exist except when a centripetal force is applied. In that context, it is "fictitious", since it's merely a product of action--reaction that makes us aware of our previously unchallenged forward momentum. > You are confusing "centrifugal force" with the real centripetal force -- > that is what you feel and "experience". The basic law of inertia is what pushes you against the door when riding in a car that's turning, and inertia is what is responsible for the force you feel. The application of a centripetal force is what gives rise to the centrifugal force you feel, which sensation is a direct result of your forward momentum being diverted, it's just a name given for the redirection of inertial, straight-line motion. Dictionary.com. The American Heritage® New Dictionary of Cultural Literacy, Third Edition. Houghton Mifflin Company, 2005. http://dictionary.reference.com/browse/centrifugal%20force centrifugal force [Open Quote] A force that tends to move objects away from the center in a system undergoing circular motion. Centrifugal force keeps the water in a whirling bucket from spilling or throws a rider in a car against the door when the car goes around a sharp curve. Centrifugal force is actually a form of inertia. [Close Quote] The above is all I'm trying to say. We feel force when our forward momentum is diverted and we experience the results of our previously unnoticed inertia. >> In a rotating space colony (such as the once-proposed L5 Colony), where >> the rotation imparts artificial gravity to the occupants within, who [quoted text clipped - 5 lines] > otherwise move in a straight line (tangential to the wall because of their > motion relative to the center of the colony). Are you saying there is no force applied to the wall by the weight of the objects and people on the inside of the wall, even though the whole point of rotating the cylinder is to impart 1g of force to everything on the interior surface of the outer wall? Even the wall itself is subjected to the outward force. What force is it that would cause the people to move in a straight line if the wall wasn't there? > The key point is to analyze the situation in an INERTIAL frame. Then > objects with no net force move in straight lines. In the inertial frame of [quoted text clipped - 3 lines] > radially outward, because they have an initial velocity tangential to the > wall where they are located. If they would move outward if the wall wasn't there, then they are exerting a force on the wall when it is there. You can't have it both ways. The wall stops their outward movement, therefore the force involved that would cause their outward movement must be considered to always be there, with or without the wall. If the cylinder didn't rotate, there would be no outward force, because it's the rotation that gives rise to that force... which is the whole point of rotating the cylinder to produce artificial gravity. Space Settlements Chapter 2 - Physical Properties of Space http://www.nas.nasa.gov/About/Education/SpaceSettlement/75SummerStudy/Chapt.2.html Libration Points: Shallow Gravity Wells [Open Quote] There are other shapings of space by gravity more subtle than the deep wells surrounding each planetary object. For example, in the space of the Earth-Moon system there are shallow valleys around what are known as Lagrangian libration points (refs. 1, 2). There are five of these points as show in figure 2-1, and they arise from a balancing of the gravitational attractions of the Earth and Moon with the centrifugal force that an observer in the rotating coordinate system of the Earth and Moon would feel. The principal feature of these locations in space is that a material body placed there will maintain a fixed relation with respect to the Earth and Moon as the entire system revolves about the Sun. [Close Quote] WEIGHTLESSNESS: PSEUDOGRAVITY IS NEEDED http://www.nas.nasa.gov/About/Education/SpaceSettlement/75SummerStudy/Chapt3.htm l#Weightlessness [Open Quote] The decision to provide 1 g to the colonists means they must reside in a rotating environment; the most feasible way to generate artificial gravity. However, in a rotating system there are forces acting other than the centrifugal force which supplies the pseudogravity. [Close Quote] I think the explanation below brings what I'm trying to say into focus: Centrifugal Force - The False Force http://regentsprep.org/Regents/physics/phys06/bcentrif/centrif.htm [Open Quote] The car tires on the road have a enough static friction to act as centripetal force which forces the car to go around the curve. The tape on the slippery dashboard does not have enough friction to act as a centripetal force, so in the absence of a centripetal force the tape follows straight line motion. The car literally turns out from underneath the tape, but from the passenger's point of view it looks as though something (a ghost force?) pushed the tape across the dashboard. If the car you are riding in has the windows rolled down, then the tape will leave the car (or does the car leave the tape?) as it follows its straight line path. If the windows are rolled up, then the window will deliver a centripetal force to the tape and keep it in a circular path. Any time the word Centrifugal Force is used, what is really being described is a Lack-of-Centripetal Force. [Close Quote] Centrifugal force is a name that defines diverted momentum, therefore there must be something to divert that momentum before any force is felt. The force that is experienced when centripetal force is applied is due to momentum. Centripetal force From Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Centripetal_force [Open Quote] The centripetal force is the external force required to make the body move in a circular path with uniform speed and directed towards the center. Hence it is a force requirement, not a physical force in its own right. [Close Quote] > Tom Roberts Be well - Pax > Are you saying there is no force applied to the wall by the weight of the > objects and people on the inside of the wall, even though the whole point of > rotating the cylinder is to impart 1g of force to everything on the interior > surface of the outer wall? Even the wall itself is subjected to the outward > force. What force is it that would cause the people to move in a straight > line if the wall wasn't there? No force is needed to cause the people to move in a straight line. Did you learn nothing from Newton? Stephen >> Are you saying there is no force applied to the wall by the weight of the >> objects and people on the inside of the wall, even though the whole point [quoted text clipped - 5 lines] > No force is needed to cause the people to move in a straight line. Did > you learn nothing from Newton? If there was no wall, they wouldn't go anywhere. Newton is in the wall. > Stephen Be well - Pax >>> Are you saying there is no force applied to the wall by the weight of the >>> objects and people on the inside of the wall, even though the whole point [quoted text clipped - 5 lines] >> No force is needed to cause the people to move in a straight line. Did >> you learn nothing from Newton? > If there was no wall, they wouldn't go anywhere. Newton is in the wall. If there was no wall, they would continue moving in whatever direction they were moving. You seem to have some Aristotlean notion that motion requires force. Stephen >>>> Are you saying there is no force applied to the wall by the weight of >>>> the objects and people on the inside of the wall, even though the whole [quoted text clipped - 11 lines] > they were moving. You seem to have some Aristotlean notion that motion > requires force. What causes motion... well, besides time? > Stephen Be well - Pax > <step...@nomail.com> wrote in messagenews:ema7jn$uqf$1@news.msu.edu... > [quoted text clipped - 3 lines] > >What causes motion... well, besides time? Nothing causes motion. Motion is an observer-dependent property and doesn't inherently belong to the object at all. Now, a *change* in motion is something else entirely. PD >> <step...@nomail.com> wrote in messagenews:ema7jn$uqf$1@news.msu.edu... >> [quoted text clipped - 5 lines] > > Nothing causes motion. Force applied through time causes motion. It doesn't matter if the motion is considered to be of the object observed or of the frame of the observer, force is involved, understood, and considered where interaction between the two is concerned. In the instance of the space colony, the force comes from the rotation of the colony that results in artificial gravity. Anything on the interior of the external wall (or any internal walls parallel to the external wall) would be subject to the acceleration imparted by the rotation. That acceleration imparts inertia to everything on the interior of that wall, which things, along with the materials composing the rotating wall itself, seek a straight-line path away from the center of rotation. > Motion is an observer-dependent property and doesn't inherently belong to > the object at all. True. It implies either the observer or the object being observed is in motion, and of course perception of motion is frame-dependent. > Now, a *change* in motion is something else entirely. Not really, motion is motion. Any motion denotes some sort of force applied in the past, even if it's the extremely distant past. If that weren't so, the Big Bang would never have been hypothesized as a result of the observed and assumed to be "outward" motion of celestial objects. > PD Be well - Pax > >> <step...@nomail.com> wrote in messagenews:ema7jn$uqf$1@news.msu.edu... > [quoted text clipped - 9 lines] > force is involved, understood, and considered where interaction between the > two is concerned. Well, that's the interesting part, because as you well know, a force applied through time can also *remove* motion -- as when you apply the brakes to get to a stop sign. But consider the fact that two different observers will look at the *same* acceleration, the *same* force, the time between the *same* two events, and come to two different conclusions about the motion. One observer will see that the car was initially going 30 mph relative to the observer and ended going 0 mph relative to the observer. A second observer will see that the car was initially going 0 mph relative to the observer and ended up going 30 mph relative to the observer. A third observer will see that the car was initially going 10 mph relative to the observer, slowed to a stop, and then ended up going 20 mph in the other direction relative to the observer. So, what was the result of the force over that interval: stopping motion? creating motion? stopping motion and then creating it again? Which observer has the "real" view of what happened to the motion of that car? > > Now, a *change* in motion is something else entirely. > > Not really, motion is motion. Any motion denotes some sort of force applied > in the past, even if it's the extremely distant past. If that weren't so, > the Big Bang would never have been hypothesized as a result of the observed > and assumed to be "outward" motion of celestial objects. And here again is an interesting point, because modern cosmology does NOT say that everything is in *absolute* motion today. The only observeration is that everything is in *relative* motion (and two things being in relative motion is observer-independent, though the *amount* of relative motion is observer-dependent), and that at some finite point in the past, all of those objects now in relative motion must have been on top of each other. PD > > <step...@nomail.com> wrote in messagenews:ema7jn$uqf$1@news.msu.edu... > > [quoted text clipped - 7 lines] > doesn't inherently belong to the object at all. Now, a *change* in > motion is something else entirely. You never learn. Not all kinematic quantities are observer dependent. Acceleration id absolute, absolutely in Newtonian Mechanis per se, and as such in GR but with qualifications. You straw man again. Force is related to acceleration, not to other kinematic quantities liek velocity or position. A force causes acceleration, which is absolute and frame independent. Velocity and position are frame dependent but they are not a direct effect of the cause. The direct effect is acceleration. Get your act together. Mike > PD > > > <step...@nomail.com> wrote in messagenews:ema7jn$uqf$1@news.msu.edu... > [quoted text clipped - 11 lines] > Acceleration id absolute, absolutely in Newtonian Mechanis per se, and > as such in GR but with qualifications. That's what I said. Motion is an observer-dependent property. Now a *change* in motion is something else entirely. Perhaps your knee obstructed your vision when it jerked up like that. PD > You straw man again. Force is related to acceleration, not to other > kinematic quantities liek velocity or position. A force causes [quoted text clipped - 7 lines] > > > PD- Hide quoted text -- Show quoted text - > > > > <step...@nomail.com> wrote in messagenews:ema7jn$uqf$1@news.msu.edu... > > [quoted text clipped - 14 lines] > That's what I said. Motion is an observer-dependent property. Now a > *change* in motion is something else entirely. Are you saying that a change in motion does not result in motion? > Perhaps your knee obstructed your vision when it jerked up like that. Perhaps, you should get examined. Mike > PD > [quoted text clipped - 9 |
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