Quote:
Originally posted by MattyX:
Quote:
Originally posted by BlueSky:
[b]
Quote:
Originally posted by Mobycat:
[b]The jet has to overcome it's weight to move forward.

So the friction of the wheels IS relevant.

If it weren't, you could walk up to a plane and push it with your own force.
Exactly. Two questions to the "plane doesn't care what the wheels are doing" group:

1. You think the wheel friction doesn't enter into it? Stick your head under one of them, since they're bearing the entire weight of the aircraft, and see what happens.

2. If what's going on with the wheels doesn't matter, try reducing their speed to zero and see what happens, even with full thrust. Trust me, you won't fly.

You guys are confusing the issue of what counteracts what to achieve flight.

Lift overcomes gravity.
Thrust overcomes drag.

BOTH must occur for flight. The wheels turning on a stationary surface allows the thrust to overcome gravity (the aircraft's weight).

Think of the law that says an object at rest tends to remain at rest unless an outside force is applied. The outside force here is engine thrust, but it's negated by the moving belt, so the object remains at rest and gravity thus is NOT overcome by lift.

The plane WILL NOT FLY.[/b]
OK, I'll try again. Wheels are simple tools designed to minimize friction. Propellors and jet turbines are relatively simple machines designed to MOVE whatever vehicle they're mounted on. No matter what the surface beneath the wheels does, as long as the wheels can perform their function and reduce friction (spin freely) the prop/turbine will power the craft forward.[/b]
Unless the surface they're on is moving in the opposite direction. laugh

So by your statement, if the surface is moving sideways, the craft will go forward?