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Ghideon

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Ghideon last won the day on October 16

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About Ghideon

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    Primate

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    Sweden
  • College Major/Degree
    M.Sc. Computer Science and Engineering
  • Favorite Area of Science
    Physics

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  1. f Thanks. Please not though that specific the sentences you quote was an example of an invalid answer. I posted that to highlight what happens when the negation is dropped per your request; without negation it allows for weddings to be held at other places (for instance indoors) even if it is a sunny day. Maybe I should have posted a more explicit sentence: Incorrect, no negation: "sunny_day ∨ garden_wedding" = "On sunny days weddings are sometimes held in the garden and sometimes not held in the garden, for instance indoors.” Correct, as per tutorial, with negation: "~ sunny_day ∨ garden_wedding" = “On sunny days weddings are held in the garden.” The tutorial's sentence disallows indoor weddings on sunny days but does not disallow garden weddings on a rainy day. The incorrect sentence (no negation) incorrectly allows indoors weddings on sunny days.
  2. Maybe the first sentences? The above, taken from the linked thread, implies as far as I can tell that Maxwell is not valid.
  3. It is explained in detail in the document, especially the part where the truth table for both expressions are compared: Extract from http://watson.latech.edu/book/intelligence/intelligenceApproaches2b1.html (emphasis mine) Maybe you could give some more detail about with step that causes trouble. Without the "not" we have the expression "sunny_day ∨ garden_wedding" instead of the tutorial's "~ sunny_day ∨ garden_wedding" That implies that there could be sunny days with weddings not in the garden and that is not what the original sentence says. Expression "sunny_day ∨ garden_wedding" is more like "On sunny days weddings are sometimes held in the garden and sometimes not.”
  4. I agree. Random thoughts, not much science below: IF (extremely big if) the far-fetched idea is correct I assume the current universe is not likely the the very first occurrence of the universe, there was many prior universes. I have no evidence that any events in any earlier universe affects us. So from a philosophical point of view; since I do not remember living the same life in an earlier universe I neglect the chance of remembering this universe if there is ever repetition. And if this is indeed the first version of the universe and memories from this universe will remain in the next one, then the next universe can't be an exact repetition. Just by having the first sentient beings basing their decisions on memories from earlier life, that would create some profound ripple effects, in addition to @joigus randomness?
  5. Probably. But more likely I tried to point out the holes in another members argument regarding outwards acceleration and I went off on a tangent.
  6. Recently I returned to a discussion after a break and I was suddenly accused of not taking centrifugal forces into account. I guess I was out of the loop for a while.
  7. Regarding circumventing Newton or regarding this specific example? One example: your deltas = 0 Implying T=0 means the firs equation equals 0. That can only happen when one or more of m, w, r is zero.
  8. You have two sets of coordinate systems in your equations and none in your picture. You mention kinetic friction above, that is not in your picture. You have one set of time independent equations (per frame of reference), example speaks of three (at least) different states. You imply from the equations that there is constant linear motion or that mass m=0 or radius r=0. That is not what the picture shows. You speak of this dimension of force on the rod. Not in your picture. Tension is not is your picture. You have argued that there is outward acceleration* in the inertial frame of reference in your example but now say tension on the rod. that means inward acceleration at all times, Outward acceleration in the inertial frame of reference implies compression of the rod. (The above is a short extract) A short and more to the point way to express how I prefer this discussion to continue: Start with something simpler. You need to be able to draw correct conclusions to be able to write meaningful equations for the example. So far that has not happened. The rest of you comment can't be addressed since the seem to describe some situation that does not exist in the example. I'll postpone any answer until more information is provided. *) https://www.scienceforums.net/topic/123261-circumventing-newtons-third-law-through-euler-inertial-forces/?do=findComment&comment=1157422
  9. <Sarcasm> Any member who would like to contribute just have to read through the 500+ posts and try to locate which exact example you mean. </Sarcasm> If you mean the following, then the equations does not match: https://www.scienceforums.net/topic/123261-circumventing-newtons-third-law-through-euler-inertial-forces/?do=findComment&comment=1156979 That does not describe what happens. Introducing tension along the rod makes this complicated; you need to account for the fact that tension is not constant along the rod. And maximum tension in the rod can't be less that centripetal force, not in the example i linked. A friendly suggestion: Start with something simpler instead or study the physics (and in this case engineering) required (doing both would also be fine). Ok, but it makes the analysis tricky when personal terms are introduced without definition. The force may not be external to the system but it is external to the rod, so again the equations are not easy to follow. But removing all non external (=internal) forces would simplify our analysis of the whole system: F=ma F=0, a=0. Done (m = total mass, F = total external forces, a=acceleration of the whole system)
  10. edit: Can you provide definitions what the variables means? x-posted; Definitions were added to the post above. This part looks strange* given the definite of T=tension of rigid rod and F centripetal force: How can the tension be greater than the centripetal force? It looks like you are mixing forces acting on different objects in the equations making it pretty hard to see if the equations have any physical meaning or not. Also note that you have added tension in the y direction, you probably mean shear stress. Note @John2020 It may help drive the discussion if you refer to exactly which example the equations are meant to describe. *) There are more issues ...
  11. Ok. Some correctly performed application of Newton will do. The tricks you have pulled out of your sleeves so far are not very impressing.
  12. Please explain what the point is. I will provide the mathematics, you will interprete it with your personal version of physics and state that calculations are wrong or have some other issue. Note that @swansont already provided the matehamtics for the inertial frame of reference, you may start by commenting on that. I think the problem is that you require your personal interpretation to be correct. It looks like you need/want fictitious centrifugal forces have physical effect and adopt the equations to that. I will provide mathematics as soon as you are past the initial step of understating the basics of centripetal acceleration. Feel free to provide a simpler example if needed. There must be many example that have the same basic properties but that are less complicated.
  13. Your mathematics does not match the picture you have provided. Maybe you should start more simple? Provide the inertial frame of reference first, and describe the steps in the equations more explicitly. Be extra careful with the transition phase. (side note: This thread has now reached the third place in the unofficial competition "speculations thread with the most answers". )
  14. No. I speak of real forces, present in any frame. The friction does not change when we change coordinate system. If you start from invalid physics and end up with invalid equations. If two real forces (forces that are not fictitious) are different in two frames of reference we know you made an error. It sounds like you try to force your misunderstanding of rotation and fictitious forces (for instance centrifugal forces) on the rest of physics. It will not happen.
  15. Cant comment unless you are more specific about what you wrote.
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