How does optimum motor speed relate to Thevenin's Theorem?

Hi so you have discovered old thevenin's THEOREM. well how did you get on with  KIRCHHOFF.
both are true about a lot of Electronic theory.
i think they say it all really.
so how does it compute to optimum motor speed well they would if they where not allowing for friction. that is where things start to fall apart heating less inefficiency and all sorts of mechanical failures like human being building the motors in the first place.  
so where you go from here a dyno mono meter would be a good place to start the physically put the motor under some sort of load and take several measurements then all the theory goes out the window.