From: fortunati.luigi@gmail.com   
      
   Luigi Fortunati domenica 08/04/2018 alle ore 01:24:36 ha scritto:   
   > Thomas Koenig mercoled=EC 04/04/2018 alle ore 09:35:02 ha scritto:   
   >> Well, you have removed most effects of what will happen from consideratio=   
   >> n; the only major effect left (that I can think of) is viscoelasticity.   
   >>   
   >> Rubber can be quite elastic for short deformations; a force applied only   
   >> for a short time, and then removed, will lead to a smaller deformation   
   >> than a force applied for a longer time.   
   >>   
   >> So, for this, the tread will be deformed a little less, so the vehicle   
   >> will rise a bit.   
   >   
   > Your answer is the exact confirmation of what I expected: the vehicle   
   > in speed tends to rise a little, that is to weigh less against the   
   > asphalt, compared to the stationary car.   
   >   
   > [[Mod. note -- The vehicle's weight will be unchanged (assuming the   
   > road to be straight & flat (neither curving-up nor curving-down).   
   > As Thomas Koenig explained, this *same* weight will lead to a smaller   
   > tire deformation at high speed.   
   > -- jt]]   
      
   It is undoubtedly true that the weight of the car in motion is always   
   the same, but the moving car distributes its weight on a wider surface   
   of the ground (with respect to the stationary car).   
      
   The tread works like a spring and then we can apply Hooke's law to its   
   compression: the compressed tread of 2 millimeters exerts at its ends a   
   force *less* than a third, compared to the same tread compressed by 3   
   millimeters.   
      
   Therefore, when the car is stationary, the compressed tread exerts a   
   force upwards of 3.   
      
   For the third principle *also* the stationary car exerts a force of 3   
   on the tread.   
      
   When the car is running, the compressed tread exerts a force upward of   
   2.   
      
   For the third principle *also* the car exerts a force of 2 on the   
   tread.   
      
   Even if the weight of the car is still the same, for the asphalt the   
   car in motion is lighter.   
      
   [[Mod. note -- The car is (by assumption) not accelerating vertically.   
   Therefore (Newton's 2nd law, F = ma) the net vertical force on the car   
   must be zero.  This net vertical force is the sum of a downward force   
   (mg) due to the Earth's gravity, and an upward force F_contact exerted   
   by the road on the car tires.  Therefore F_contact must equal mg.   
   By Newton's 3rd law F_contact must be equal in magnitude to the   
   downward force the car tires exert on the road.   
      
   Since F_contact = mg, this force is independent of the car's speed.   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)