The Swing of a Pendulum

Discussion in 'Pseudoscience Archive' started by Motor Daddy, Jan 3, 2013.

  1. Motor Daddy Valued Senior Member

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    Two cars are driving down a highway in the same direction at the same constant velocity, one in front of the other. There is 20 meters between the cars. The initial velocity of the cars is constant, and the distance between the cars remains constant at all times. There is no relative motion between the cars as they travel down the highway.

    Each car has a pendulum suspended from the rear view mirror to indicate changes in velocity.

    If the cars were to simultaneously accelerate at the same rate, the pendulums would swing simultaneously. The distance between the cars would remain the same.

    Q: If the pendulums are swinging and the relative velocity between the cars remains the same at zero, then what velocity is it that the swinging pendulum is indicating a change in?
     
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  3. AlphaNumeric Fully ionized Registered Senior Member

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    The change in velocity is the change from the inertial frame the cars find themselves in initially to the ones they find themselves in at the end. Each car knows they have experienced acceleration and can tell how much their velocity has changed. They cannot say what their velocity changed from and what it is now since there is no absolute frame, though if they picked a frame to give their velocity relative to then they can talk about velocity with respect to that.

    The fact the cars always view one another are precisely the same distance apart doesn't mean their velocity doesn't change. Two people next to one another on a rollercoaster know if they are on the ride (accelerating along the track, around corners etc) or sitting in the station, even though they are always at the same position relative to one another. You don't seem to realise that they are not the only frames you can consider in relativity. A third frame, an abstract one which doesn't actually have a person to go with it, can still be used.

    Like I said in the other thread, you'll be taken more seriously when you make it clear you've bothered to learn some relativity. Constantly trying to come up with what you think are contradictions in relativity, without actually knowing what relativity has to say, is clearly a way of squandering vast amounts of your time. If you have such time to waste and nothing more productive to do with your existence then fine but that's a pretty sad state to be in.
     
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  5. Motor Daddy Valued Senior Member

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    The pendulum indicates a change in absolute velocity. The pendulum is non-responsive to changes in relative velocity between the two cars caused by the other car's change in motion. Since the pendulum indicates a change in velocity, and the relative velocity doesn't change, the pendulum is indicating a change in absolute velocity.
     
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  7. Motor Daddy Valued Senior Member

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    I'm just trying to figure out what you mean by wasting time. How do you waste time? Doesn't time always elapse in full? Isn't it impossible to waste time?
     
  8. Motor Daddy Valued Senior Member

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    Are you acknowledging that each car has its own velocity and that each car's velocity changes as it accelerates? Sounds to me like what you are describing is an absolute motion of the car in space, with its own velocity, independent of other objects.
     
  9. origin Heading towards oblivion Valued Senior Member

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    Just out of curiosity, did you even read AlphaNumeric's post? If you did, how is it possible you could not understand it?
     
  10. AlphaNumeric Fully ionized Registered Senior Member

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    Each car has a velocity. Each car experiences acceleration, which changes its velocity.

    No, I'm describing a change in velocity. There is an inertial frame associated to the cars at the start, namely the one associated to their rest frame. No need for an absolute frame. The cars accelerate and then stop accelerating, putting them in a different rest frame. Two frames, moving relative to one another, no requirement for an absolute reference frame.

    Reference frames are like coordinate systems. In the first inertial frame the cars at at rest initially and at some speed v at the end. If we worked in the end reference frame then the cars start at speed -v and end at speed 0. If I worked in some other reference frame then they start at speed V and end at speed V+v. Where they at any moment in time requires careful calculation using Lorentz transforms and worldlines but they don't require the use of an absolute reference frame.

    This is precisely the point I have made several times to you. You don't know what SR says, you don't know how references work within it, you don't understand any of it and thus you just jump to utterly unsupported conclusions based on your ignorance. You obviously don't have the intellectual honesty (and I doubt you have the intellectual capacity even if you were intellectually honest) to find out what SR actually says or to stop jumping to utterly unsupported conclusions. As such you're not worth spending significant time on. Fortunately your laughable attempts at 'disproving' relativity are so terrible, thanks to your shortcomings as a physicist, little effort is usually required to blow them out of the water.

    As origin says, did you even think about what I said or did you just try to find a sentence which you think you can twist into something for your own gain? If you know you're doing it then you should realise how obvious that behaviour is. If you don't realise you're doing it then I'll tell you now, it is obviously a dishonest action on your part.

    I really hope you're attempting to be humorous or you're not a native English speaker. The alternative is that you're even more dense than I thought (and that's pretty bad already).
     
  11. Motor Daddy Valued Senior Member

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    Let's just stick to this statement for now, since the rest of your statements are basically what you commonly refer to as, how you say...a waste of time? lol

    You claim you recognize that each object has its own velocity. What is that velocity in relation to?
     
  12. RJBeery Natural Philosopher Valued Senior Member

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    Each car has some velocity according to an arbitrary measuring frame; call it V1 and V2. Don't latch on to AN's use of the word "a" like this value is set and invariant. Without mentioning the measuring frame we cannot assign the specific velocity values. We CAN make a declaration that these velocities are changing, though, when the vehicles experience acceleration. This is true for ALL measuring frames.
     
  13. Motor Daddy Valued Senior Member

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    There is only 2 cars. If you like we can change the cars to rockets. Forget the road. There is two rockets with rocket engines, traveling one behind the other at the same speed. The distance between them remains constant at all times. You have no concept of absolute velocity so the only thing you have is relative velocity to work with. All your measurements are dependent on each of your motions. There is no change in distance between the rockets at all times. The relative velocity is always zero. No relative motion. None. Zilch. There is no change in velocity the entire time. There is no change is ft/sec per second.
     
  14. RJBeery Natural Philosopher Valued Senior Member

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    OK, perhaps your point is that if the rockets were the only objects in the universe and we accelerate them then...how can we declare that their velocities have changed? The answer is that you could not accelerate them without changing their velocities relative to something, which in this case would be the exhaust spewing out the backside of them. In other words, the only way the acceleration can happen is if you have something else in the Universe to allow (and measure) the acceleration.
     
  15. Motor Daddy Valued Senior Member

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    The pendulum doesn't lie! The pendulums swung simultaneously! You have a contradiction unless you acknowledge the absolute velocity change is what caused the pendulum to swing!
     
  16. RJBeery Natural Philosopher Valued Senior Member

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    You aren't reading what I'm saying. You CANNOT make the pendulums swing unless you actually do have other objects in the Universe which allow you to accelerate. In the case of the rocket ships, it would be exhaust.
     
  17. Motor Daddy Valued Senior Member

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    I am not measuring the speed of the exhaust, I am measuring the distance between the two rockets. The distance between the two rockets stays the same at all times, even when the pendulums are swinging!

    Do you know what acceleration is? Acceleration is the rate of change of velocity. The pendulum indicates a change in velocity. But you have no change in velocity, as the distance between the two rockets remains the same at all times. No relative velocity and no change in relative velocity means no acceleration. But there's still that pesky swinging pendulum that keeps standing in the way of your "reality." (rolls eyes) I hate it when that happens!
     
  18. RJBeery Natural Philosopher Valued Senior Member

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    Then I don't understand your point. Are you claiming that the rockets' velocities do not change when the pendulums move?
     
  19. Motor Daddy Valued Senior Member

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    I claim the rockets each have absolute velocities, and the pendulum indicates when those absolute velocities are changing.

    You claim that there is no such animal as absolute velocity, that all velocity has to be relative to something. There is a rocket in front of you and there is no relative motion between your rocket and the rocket in front of you. You MUST claim the velocity is zero, and remains at zero the entire time. Then there's that pesky pendulum that keeps laughing at you and ruining your perfect theory.
     
  20. RJBeery Natural Philosopher Valued Senior Member

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    Yes, the velocity of rocket A is zero relative to rocket B. That "pesky pendulum" is also changing for your reference frame which is what would allow us to ignore it for rocket A. An non-inertial reference frame is odd. To see why, how about you just put rocket B under acceleration and then conclude that rocket A's velocity is changing magically?
     
  21. Motor Daddy Valued Senior Member

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    See, that's just one more piece of bling that my theory has that Big Al's doesn't. My theory recognizes that each object in space has its own velocity. My theory also recognizes that there is also relative motion between all the objects in motion in space. In simpler terms, my theory does both relative velocity and absolute velocity and big Al's just does relative. Big Al missed the big picture!
     
  22. RJBeery Natural Philosopher Valued Senior Member

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    Actually...I agree with you. I would prefer your world where velocities are absolute and exceeding c is possible. Unfortunately, Nature does not agree with you. You aren't actually arguing against AlphaNumeric, you are a small voice screaming at the tsunami of scientific evidence that says your view is not correct.
     
  23. Motor Daddy Valued Senior Member

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    In the end all that matters is that I understand it. It would be nice if everyone understood and agreed with it, but that is not gonna happen. I understand it and that is the important thing. I tried to teach people but they didn't listen. Oh well, I tried and I'll keep trying.
     

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