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Rice University gets Newtons 3rd Law wrong

  1. Dec 7, 2016 #1
    I couldn't remember which number was which in Newton's laws of motion, and so I clicked the first link I found, but to my amazement it seems that while Rice University got the number right, they got the facts of how it works wrong. Ironically it seems they have made the same mistake as that famous article by the New York Times ridiculing Robert Goddard. Unless it is me who has made the error.


    The rocket's action is to push down on the ground with the force of its powerful engines, and the reaction is that the ground pushes the rocket upwards with an equal force.

    http://teachertech.rice.edu/Participants/louviere/Newton/law3.html
     
  2. jcsd
  3. Dec 7, 2016 #2

    phinds

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    You are correct. They got it right in the illustration but the text is nonsense and is in fact exactly the same POV as in that infamously stupid statement that you mentioned from the NY times.
     
  4. Dec 7, 2016 #3

    russ_watters

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    If they are going to explain it wrong, the least they can do is be consistent and show it wrong in the diagram too! The ground isn't even drawn in the diagram, so how can it be applying any forces on anything? That's wrong-squared in my book.
     
  5. Dec 7, 2016 #4
  6. Dec 8, 2016 #5
    Well they say this...
    An object in motion continues in motion with the same speed and in the same direction

    Usually it is expressed as 'in a straight line', which I think is more correct because it does move in a straight line but in curved space, if you say 'same direction' then that could technically be incorrect because the direction might be in a straight line but space may curve. For example the famous Eddington measurement of the position of a star near the sun. Not sure about this though.
     
  7. Dec 8, 2016 #6

    phinds

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    Space is not curved. It is spacetime that follows Riemann geometry (and therefor appears "curved" when viewed from the POV of Euclidean geometry).
     
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