Can the Plane Take-Off?

[sciguy125]

Originally Posted by greencactus3

correct. which is why you can say either side is correct. if you ignore conveyorbelt limits

I don't understand your basis for that. Let's go back to Elgin's equations that I've been working with:

Fy = Fl + (-Fg) - Fl is lift force, Fg is force of gravity
Fx = Ft + (-Fc) - Ft is force of thrust (engines), Fc is force of conveyor

and some I'm adding:
F = ma <- solve for a
a = F/m <- integrate with respect to t
V = (F*t)/m
Vx = [(Ft - Fc)*t]/m
Fc = umg = uFg - u is coefficient of friction

Vx is a function of Fx. And we know Fy is a function of Vx. So, the only thing we really care about is Vx. If Vx > 0, we'll have Fl > 0. If Fl > Fg, Fy > 0.

So, how do we get Vx > 0? Well, Fx has to be >0. This is true as long as Ft > Fc. We know that u << 1. With this, we'd only have to provide some Ft that is some small fraction of Fg.

As you can see, the speed of the conveyor never comes into play.