"Bob Martin" wrote in message
...
Darkwing wrote:



Nope the plane won't take off.


You'd better not just be trolling...

Friction generated by wheels is almost negligible. Even for very large
aircraft like a 747, wheel friction is nearly constant, regardless of
speed (at least at sane speeds). It only depends on the amount of force
pushing down on the wheel.

So let's look at all of the forces acting on this airplane. In the
horizontal direction, we have:
Thrust from the engine (nearly constant at these speeds)
Aerodynamic drag (goes up as the square of speed)
Wheel friction (again, nearly constant)

For any object to accelerate in a given direction, the total force acting
on it in that direction must not be equal to zero. For a normal airplane,
on a normal runway takeoff, thrust must obviously be greater than the
other two forces, since we see airplanes take off every day. Even at the
moment of takeoff, aerodynamic drag may have increased, but the airplane
still has a fair bit of excess thrust, and (assuming you don't pull up too
steeply) will continue to accelerate.

So now, let's put the plane on the treadmill. Once again, the ONLY forces
acting on it are thrust (which stays the same), drag (which still
increases as speed squared, and wheel friction (which, again, IS CONSTANT!
no matter how fast the treadmill runs, until we start talking about silly
cases like 5000mph treadmills). Sticking to sane, airplane-like speeds
for the treadmill (80-160mph or so) We see that, once again, thrust is
greater than the other two. Therefore, the plane MUST accelerate.

I'd like to also point out that I have tried this on an actual treadmill
with a small model airplane. It takes right off, no problem. Now I just
need to go fin

I am a regular on RAP, not a troll.

Show me video and I will believe it, if the plane is not moving relative to
the wind then the wing isn't making lift. I have ran on treadmills and I
never felt a "wind" blowing in my face.

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DW