Airplane physics question

Let's think of it this way. An exercise bike at the gym.. your pedaling away at 20 mph on the bike..there is zero wind..even though you are doing 20mph.

You jump on your road bike..and you do 20 mph..you will obviously feel wind against you.

Even though it would be impossible to exactly match the speed of the airplane instantly.. the question doesn't allow for that. The speed of the conveyer matches the speed of the plane AT ALL TIMES. It doesn't move forward. It doesn't accelerate faster than the conveyer which it would have to in order to create lift.

The only way for the airplane to fly, is if it moves faster than the conveyer. If the conveyer speed and aircraft speed are the same..but in opposite directions..it will not move.

 

I didn't really expect to end this old thread today with the video I posted, although it has the potential to do so, by briefly and directly explaining views and why they conflict. But anyway it seems that everyone is so self centered in their own position that this will go on for many years. Long live this thread!

 

Yes, exactly.

Of course it's made to be a trick question, how many people have said "I don't go anywhere when I run on a treadmill"

Looking beyond that, just trying to find a way to answer the question as it was asked.

For example,

Plane moves forward 5mph. Conveyor matches 5mph (which also zeroes wheel rotation) but wheel and conveyor speed match.

Plane stops conveyor continues. Now the wheels are spinning backwards at 5mph.

Would that not be opposite direction of rotation?

 

Completely irrelevant.

Stand on a moving walkway wearing roller skates and strap a rocket on your back. Tell me you are stationary.

Said in another way. Moving walkway is moving south. You are on it wearing roller skates.

Could you not be pushed north against the movement of the walkway from someone beside it?

That is thrust and that is how aircraft operate.

 

Post 2727

As the question is written..as confirmed by the video..the plane does not fly. In the REAL world.. where the question does not take place..yes it will fly..because it will eventually overcome the speed of the conveyer and lift off..

 

Well either the opposite or the same. The top of the wheel goes one way the bottom the other.

 

It does, but cancelling wheel rotation would also turn it opposite of rotation.

 

The fake idiot pilot in the video doesn't understand it either. The plane (unlike a car) does not rely on its wheels to push the it forward, it relies solely on its engines. The only way the conveyor belt could have a non-negligible effect on the forward motion of the plane is if it were covered in 3 feet of unset concrete. That would impart some significant drag on the plane but still not enough to overcome the combined thrust of 4 turbine engines.

 

Not to mention the question is posed differently. (opposite direction of craft rather than opposite direction of rotation)

 

This is embarrassing man…. I feel like this whole thread is to make fun of a unique community (FChatters) who are usually intelligent in one aspect of life/career and think it translates to everything = hilariously overly confident people.

Simply people…. This thread is so embarrassing. It should be over. A plane flies from airspeed, not ground speed. The prop or turbines produce thrust, not the tires/wheels. If a plane at full throttle goes 100 knots air speed, and a treadmill thats a mile long beneath it is going 100 knots backwards, the plane with engine off would roll backwards with it (at same speed of treadmill minus some drag), but as soon as it’s full throttle it would pull nearly 100 kts forwards. The tires may be rotating at 200kts equivalent, but the airflow over wing would be 100kts. Theoretically, maybe 99.5 kts forward as the tires and wheel bearings may produce some super slight resistance from contact with the treadmill.

The treadmill is almost irrelevant, no different than the ground, because the planes speed is from the prop or turbine.

Here’s something interesting, if the treadmill is going 100kts in the SAME direction as the plane, and the plane is at full throttle with max air speed of 100kts, then it would NOT be going 200kts, it would still be only going 100kts, well maybe 100.5 kts, but you get the point. A car driving on a 30mph treadmill going the same direction as a 30mph car would go 60mph (assuming it’s aerodynamically capable) because the tires produce the forward movement on car.

Tires to ground = thrust on car
Prop/Turbine to air = thrust on plane, air over wings = lift on planes
-the tires to the ground in a plane is virtually irrelevant for both how much air is going over the wings (lift) and how much forward thrust it produces (prop/turbines).

I’ve taken planes off almost straight up like a helicopter from heavy headwinds, sporty light planes albeit. I’ve flown backwards over the ground many times with an airspeed of ~35kts, so the plane is physically moving through the air but still moving backwards over the ground. In this scenario, just imagine I had a treadmill going any direction underneath me (forward, backwards, left, or right), ID STILL BE FLYING REGARDLESS OF THE TREADMILL.


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Simply put, the treadmill could be going forwards, sideways, or backwards at any speed it wants and the plane would still fly. The plane would pull over the treadmill (with minor resistance) and accelerate in a forward movement in relation to its prop/turbine regardless of what the treadmill is doing underneath. Assuming calm winds, the plane would still need a ground roll before accumulating enough speed for takeoff. If takeoff speed is 80kts, and the plane has a headwind of 80kts, and the power is set to what normally produces 80kts, then the plane would takeoff like a helicopter ABSOLUTELY REGARDLESS of what the treadmill is doing underneath (left, right, forward, Backwards, etc - and… if the treadmill matches speed of tires rotating then in this scenario the speed of treadmill would be 0kts).

All these interpretations of the nuances of the question are stupid. The plane would fly, assuming it has enough room/treadmill length ahead to reach takeoff speed, near regardless of whatever direction or speed the treadmill is going.

Anyone who thinks otherwise really needs to study simply physics and aircraft aerodynamics/operations. The bigger issue is why this is 3,000 posts. It’s really sad to see people so opinionated and confident that they don’t look something up before being so confidently wrong.

I feel like this thread needs heavily studied by some psychology majors…. The issue isn’t that people don’t know something, the issue is that despite well written answers, people still stick by their blatantly wrong opinions without doing basic thinking or studying. (Not that this is complicated either)


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Dude… this is embarrassing. A road bike is putting power output down from tire to road. A plane does so by prop/turbine to air. The treadmill underneath is irrelevant and the plane will move forward and fly. My god…. How confidently wrong people can be.

I’m going to use this question in interviews to see people’s critical thinking and basic problem solving capabilities. This is embarrassing.

Think about standing on a running treadmill with roller blades on. You put a wench on the wall that pulls at 1mph. You can hang onto the wench with the treadmill going backwards 30mph and the wench will still pull you forwards by 1mph (with minor incalculable wheel resistance decrease maybe). THE PROP/TURBINE IS THE WENCH.


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Winch on the wall pulls at one mile an hour..treadmill matches 1 mile and hour in the opposite direction..do you move forward?

 

Yes lol, you move forward by about 1mph. If one is standing in an RC car going 1 mph forward and treadmill 1mph backward, then you’re holding still over the ground.

Idk why this is a complicated question. It’s totally irrelevant what the treadmill is doing (other than minor drag from the freely rotating tires); the plane will fly…. Assuming there is enough distance to build up enough airspeed. Distance could be 0ft if it had enough headwind to take off vertically, again, regardless of the treadmills speed or direction underneath.

This is utterly simply. It’s quite embarrassing (to all humanity) how this has lasted 3,000+ posts


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Imagine a plane that is already flying. Then you sneak up to it wearing a jet pack and you have a belt sander in hand. You put that belt sander up to the tires, spinning the tires in the opposite direction of flight, does it immediately fall out of the sky? Lol…..


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You are reading WAY to much into this. What you say is true. But as the question is written it does NOT allow for that. The conveyer INSTANTLY matches EXACTLY the speed of the AIRCRAFT at all times in the OPPOSITE direction. Of you take the question as WRITTEN. The aircraft STAYS STATIONARY. IN THE REAL WORLD..it Flies. The question is a basicly a trick question. Gawd..stop taking this so serious and calling people idiots. You look like a damn cry baby..

 

You’re a great representative of this thread; so confident, yet so wrong. You should read the question again… so funny how you put “aircraft” in all caps yet the question says wheels and its rotation. Lol…. Sad man, sad and embarrassing.

The treadmill matches the speed of the wheels, and it specifically clarifies the wheel’s rotation and not the wheels relative position to the ground.

I’m not calling you a crybaby or an idiot, but it’s surely not me of the two of us.

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Since rotation is a vector, if the treadmill were moving opposite, it would be perpendicular to the orientation of the aircraft and rip the landing gear off sideways.

 

And the way I interpret the question (well how it’s factually written), the wheel would never spin but the plane would still move forward in the air and fly. Since the treadmill is magical and matches the wheel’s rotation oppositely immediately, the plane will still move forward in the air with thrust from prop or turbine and the treadmill would rotate oppositely at the exact same rate meaning the tire/wheel would never spin, but the plane would still gain airspeed.

The treadmill is absolutely irrelevant…. My jet pack man with a belt sander spinning the tires of airborne planes should help understand this.


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Again, the thrust of the prop/turbine would pull the plane forward regardless of the treadmill underneath going forward, backwards, or sideways in relation to which way the tire naturally would spin. Sure, there’s a minor amount of drag to the tire (and therefore aircraft) and if treadmill is going sideways, it would bald spot the tire or even pop it but the plane would still gain speed and fly. I’ve seen planes take off with flats throwing sparks, but now we are way off topic.

The plane would fly. Fact.


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Not even close. A treadmill moving sideways at rotation speed would instantly collapse all the landing gear and the plane would turn into a fireball.

 

#2742 is for you. I’m done with talking on this thread for now. Nothing for me to gain here. However, you seem to have great room for personal-gain, such as learning to confirm facts (such as re-reading the actual question) before doubling down on your opinion that is being challenged by well articulated logic and reasoning, and especially confirm facts prior to throwing insults. “AIRCRAFT” Lol


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Its depends from the kind of an aircraft's takeoff. If a takeoff is horizontal, the air craft will stand on the place, if a takeoff is vertical, the aircraft will fly.

 

LMAO, how can you be serious?

Have to agree that this is hugely embarrassing. Really not worth responding to this thread if questions like this are posed ^

 

He's is not so wrong. The task is an Internet meme, without exact conditions. If the speed of the aircraft = the speed of the treadmill, the aircraft will not fly. The aircraft's speed here is a speed of the wheels, turning around, but not the aircraft's body. Only vertical takeoff.