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Originally Posted by R1oldguy
JK,
show me in the original post where it says the plane has thrust or forward motion.
To me, it is merely stating that the ground speed would be zero
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Ok, oldguy. Follow along...
Original post -
"The plane
moves in one direction, while the conveyer
moves in the opposite direction"...
The plane MOVES! Without movement, the conveyor would not move, either.
But the key here is that it is an airplane. This question has been widely distributed on car and motorcycle enthusiast boards for years. Here is where our subtle bias shows. We tend to think of these things in terms we understand, cars and bikes, which are propelled by their wheels.
If the plane achieved its ground speed by traction and thrust from its wheels (like a car or bike) its speed relative to the atmosphere would indeed be 0mph and no lift or airspeed would result. The conveyor would effectively cancel out the wheel speed and the plane would not move.
However, the wheels on an airplane are not a factor here! They simply spin, in this case at twice the speed of the plane. The conveyor matches the velocity of the
plane (not the wheels) which is propelled forward through the air by thrust from its engines against the atmosphere. Not against the ground (or conveyor) through the wheels.
When the plane reaches a takeoff speed of 100mph for example, the conveyor is travelling 100mph in the opposite direction. Combine the forward speed of the aircraft and the backward speed of the conveyor and you get 200mph at the wheels. If you had a speedometer connected to the wheels, it would read double that of airspeed of the plane in this conveyor examle.
Regardless, the wheels of the plane have nothing to do with the forward speed of the plane.
Does this help explain the riddle or make it more confusing?
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