From: tjroberts137@sbcglobal.net   
      
   On 11/15/17 3:50 PM, Luigi Fortunati wrote:   
   > Tom Roberts mercoledì 15/11/2017 alle ore 09:16:36 ha scritto:   
   >> The reaction to the centripetal force of the above rope pulling on the   
   >> stone is simply the tension of the rope pulling on the hand.   
   >   
   > The tension of the rope pulling on his hand would not exist if there was not   
   > a rock FORCE on the rope to make it "tense".   
      
   Certainly. The rope pulls on the rock and makes it deviate from a   
   uniform straight line. In accordance with Newton's third law, the rock   
   pulls on the rope, giving it tension.   
      
   >> But you also seem to be confused about the reality of "centrifugal force"   
   >> and the utter impossibility of it to "cause" anything.   
   >   
   > Centrifugal force causes (for example) the "real" effect of the Earth's   
   > crushing to the poles and its enlargement to the equator.   
      
   The earth is indeed oblate, with larger radius at the equator than at   
   the poles. This is not caused by "centrifugal force". This is caused by   
   the strain induced in the rock at the equator, because the rock tries to   
   go in a uniform straight line, but is diverted by gravitational force   
   (and cohesive forces within the rock). Ditto for water at the equator.   
      
   "Centrifugal force' does not model any physical phenomenon, and thus   
   cannot be said to be "real". It is a FICTION, a mathematical convenience   
   that permits one to apply Newton's laws in rotating (non-inertial)   
   coordinates.   
      
   Tom Roberts   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)