There is an airplane on a runway. The runway is such that whenever the plane starts to move forward it slides?

Question

There is an airplane on a runway. The runway is such that whenever the plane starts to move forward it slides in the opposite direction with equal speed. Will the plane ever fly?

Answer 1

Brad J is right! It's only he just didn't make his point clear enough.

It's the air the plane pushes against; the wheels are passive in this case and they will spin twice faster than in the case on an immobile runaway.

Figure-out a man in a wheelchair on a conveyor belt which moves "backwards":
1. If that man tries to move himself by spinning the wheel, then he can't get himself moved if the "backwards" speed equals the "forwards" one.
2. Just throw that man a rope he can grab. In order to appear as staying still he just has to have a grip on the rope without really pulling it - but the wheels must of be spinning as it's the conveyor belt which does so; as soon as the man starts pulling the rope actively - whatever slow - he will be moving and the wheels will spin even faster.

As you can see, whatever fast the runaway might go "backwards", that won't stop the plane moving "forwards"; that "backwards" motion is ineffective!

Answer 2

Brad J is wrong.

The others are right.

Lift comes from airflow over the wings. If the runway slips back so that the plane gains no forward motion then there will be no airflow, so no lift.

However, it is hard to see how you would engineer this setup because, as others say, the aircraft engines yield momentum relative to the air not the ground (the wheels are not powered).

Answer 3

in order to fly a plane needs air to flow over its wings at high speed. if the plane cannot taxi forward it cannot take-off.

Answer 4

Do you mean the plane is on a big "treadmill"?

If so, then no, it will not fly. Relative to the air, the plane is still stationary.

Answer 5

yes, because the planes propulsion is not in the wheels.