From: niklas.holsti@tidorum.invalid   
      
   On 2020-10-25 1:48, JF Mezei wrote:   
   > On 2020-10-24 03:02, Niklas Holsti wrote:   
   >   
   >> If the orbiting object is in a circular orbit, the force acts   
   >> perpendicularly to the motion and so does no work.   
   >   
   >   
   > Changing direction of travel is "no work" ?   
   >   
   > If I am on a hockey rink, and a puck is coming at me and I wish to   
   > change its course so it ends up in the goal, I need to apply force to   
   > change its direction or travel, even if afterwards, it travels at the   
   > same speed as before.   
      
   Force yes (apart from the GR idea of travelling along geodesics), work no.   
      
   Stick a pole in the center of an icy lake, tie one end of a rope to a   
   swivel on the top of the pole and the other end around your waist. Put   
   skates on, stretch the rope, and work up some speed (that takes work),   
   then just glide along. The tensed rope will keep you circling around the   
   pole, with constant centripetal force and a constant speed and no more   
   work, until friction brings you to a stop, or you get bored.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)