In the case of the glider I don't know if my reasoning is correct but I would interpret the pulling force of the tug as the thurst of the glider.
Yes, but in this case the "thrust" is never directed on the vertical axis, as the cable is pulling only horizontally (the glider normally lifts off before the puller... so the thrust in that case would have a little vertical component... towards the ground!)
It doesn't matter to me who is providing the force but the force is there beacause without it it won't move.
True
Besides that when you talk about an endless runway, I could disagree with that because if we have a symmetric airfoil the airplane will never climb no matter the speed it's rolling at.
Even if we have an asymmetric airfoil, accelerating to the point that the aircraft needs an AoA of 0.5 degrees to lift off doesn't seem to me the usual take off technique so please lets stick to the real world.
Ahahah Good catch!
but if you don't consider a simmetric airfoil, then the "theoretical case" can work out.
Ok then let's work on the usual take off technique....
Engine failure after V1, you loose one engine, but you keep on accelerating to the same speed (v2) and normally you have a shallower pitch angle
It is that way, because you have now less thrust to counteract the same (2 engine case) drag.
If you follow your tought, then in this case we should pitch more, so to have a bigger thrust vector towards the sky, right?
