Trick question

[Gumbo Man]

i will be by at lunch on wednesday

👍👍

[rolylane6]

No. If the belt is moving backwards the exact same speed as the plane is moving forward the wheels wouldn’t rotate.

No. If the belt is moving backwards the exact same speed as the plane is moving forward the wheels wouldn’t rotate.

The OP says they are moving the same speed in opposite directions. It doesn't say the belt is moving backwards. I take that to mean, one is traveling clockwise, the other counterclockwise. If, so that would have them both rotating at whatever speed the other is rotating but in opposite directions, but they would be rotating...unless both stopped.

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[rjtkdplus]

Yep, you proved it! People really will argue about anything!

[brokeno]

F j b

[bpa556]

No. If the belt is moving backwards the exact same speed as the plane is moving forward the wheels wouldn’t rotate.

Yes they would.

In the OP scenario, engine thrust attempts to push the plane forward. Gravity holds the plane to the ground (on its tires[emoji6]) since there is still insufficient forward movement to create enough lift to overcome it. The magic conveyor somehow senses the revolution of the tires and begins spinning in the opposite direction at the same speed. As engine thrust increases, the conveyor senses the attempted increase in tire revolutions and instantaneously increases speed to counter.

To many minds here, the result is the plane remaining perfectly in place while the tires run at very high revolutions on the conveyor. The plane cannot move forward, thus cannot achieve sufficient lift to overcome gravity and take off.

The dilemma is that the engine thrust is pushing against the atmosphere, not the ground. This means the plane will move through the atmosphere, regardless of wheel speed. The opposing conveyor just means the tires will be spinning at double the normal RPM when lift speed is reached. I hope someone greased the bearings…


In either case, the tires will spin.


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[JackRyan]

No momentum from plane = no wind = no lift on wings

I agree with this. The jet engines have to create forward movement in order to create lift. But if the conveyor belt is really matching the wheel's speed in the opposite direction all the time then the plane is never going to move forward. The conveyor belt obviously has to speed up to match the forward force of the thrust from the engines.

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[JackRyan]

If someone pushed you from behind then you will move forward. I don't care how fast the tread mill moves and the wheels don't either.

Not if the conveyor belt spread up at the exact speed of the wheels of the skate board. You would remain stationary no matter how hard someone pushed. Assuming you don't fall off the skateboard. [emoji23]

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[tvc184]

Wind has to be passing over the wings to create lift…
The only way a plane lifts is if it’s going fast enough for the wind speed over the wings to create enough lift to overcome the weight of the plane. . Stall speed!

Think of it like a kite with no wind, except a kite is stationary so it needs wind to lift it, a plane creates its own air speed (wind) through thrust.

Mad hatter is dead on about the 500mph head wind


If the conveyor can keep up, it would have to spin so fast that the tires are creating enough friction and counter force to keep the plane in the same spot… unlikely..


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No because the wheels are free spinning and do not provide thrust. The struts and wheels merely hold the aircraft off of the ground. Free spinning wheels can’t keep an aircraft from moving forward. The wheels will simply spin faster.

[tvc184]

If a truck was pulling a glider and the truck had to reach a speed of 50mph to get the glider (with no independent thrust) and the runway/conveyor was also moving at 50mph, the glider and truck would remain stationary.

That is because in that scenario, the wheels from the pickup are providing the only thrust/motion so if the truck remain stationary due to a conveyor, so does that glider.

If the 747 was being towed by a vehicle to takeoff speed, then yes the the conveyor at the same speed would stop the motion.

NEWSFLASH: 747s aren’t towed.

[tvc184]

The paradox or real question from the scenario should be (if followed exactly by the question) how many mph would the conveyor be moving at the takeoff speed of about 200mph?

1,000mph?

10,000mph?

[Smokeater]

It would still take off but the wheels would be spinning faster than normal

Yep, just grease the wheel bearings real good cuz after a certain point, that plane is leaving no matter what treadmill it's on.

[bullets13]

I agree with whoever’s correct.

[rolylane6]

Not if the conveyor belt spread up at the exact speed of the wheels of the skate board. You would remain stationary no matter how hard someone pushed. Assuming you don't fall off the skateboard. [emoji23]

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Wheels can spin and slip/slide at the same time. Just because they are spinning at the same speed as the conveyor does not mean they won't move forward due to slip

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[tvc184]

I agree with whoever’s correct.

You can jump on my bandwagon.

[Old Bald Guy]

No because the wheels are free spinning and do not provide thrust. The struts and wheels merely hold the aircraft off of the ground. Free spinning wheels can’t keep an aircraft from moving forward. The wheels will simply spin faster.

Correct except that the conveyor is moving the same speed in the opposite direction so the wheels won’t be turning.
** My bad the wheels will be turning 2X the speed of the plane and conveyor.