From: heathjohn2@gmail.com   
      
   On Monday, October 2, 2017 at 4:26:22 AM UTC-4, Lawrence Crowell wrote:   
   > On Friday, September 29, 2017 at 8:21:02 AM UTC-5, John Heath wrote:   
   > > A car is moving at .1 c. The tire on the road at 6:00 o'clock , bottom ,   
   > > is moving at 0 c as it is touching the road but at 12:00 o'clock , top ,   
   > > the tire is moving at .2 c twice as fast as the car. Does this mean the   
   > > car is limited to speed .5 c as at this speed the top of the tire will   
   > > be moving at c twice as fast as the car ?   
   >   
   > Tom Roberts has the right idea. The Lorentz transformations of dx   
   > and dt are   
   >   
   > dt' = gamma(dt - vdx/c^2)   
   >   
   > dx' = gamma(dx - vdt) --- gamma = 1/sqrt{1 - (v/c)^2}.   
   >   
   > Now for dx/dt = u compute dx'/dt' to get the velocity addition   
   > formula. You can see that you can't add up velocities so they are   
   > greater than c.   
      
   Yes but in this case it is a rigid wheel that is being mechanically   
   forced to move twice the speed of the car.   
      
   [[Mod. note -- The author is mistaken.  It's actually a rigid wheel   
   	[we're assuming a gedanken wheel which is indeed   
   	rigid, and we're ignoring the Ehrenfest paradox]   
   whose top is being mechanically forced to move at a speed-of-car   
   speed *with respect to the car*.  As a number of people in this   
   thread have pointed out, velocities don't add the same way in special   
   relativity that they do in Galilean relativity, so the top-of-wheel   
   point is NOT moving at twice the speed-of-car with respect to the   
   road.   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)