Lift happens because of the shape of the wing and how it is "cutting" through the air. If the wing is going 0 mph (as it would be in this scenario), then no lift is created. So, if no lift is being created, is the plane going to "rise" into the air because the wheels are going nowhere at 120 mph?

I say no.

 

Thrust moves the plane viea the air... not the wheels.


edit/ would be nice if we had some flight info.

 

no..plane can't take off,what ever forward motion the plane is ataining, is lost due to the convyer belt matching it, in reverse, two cancel out, and the plane sit's....air flow under the wing creat's lift, air flow over the wing pushs the plane down...in the air the two cancel, creating a balance ( flight ) once in flight you don't need a engine to keep going ( gliders )...elevators push the plane down, flaps push the plane up...

 

There are two boats tied for "fastest boat on the lake". One is your standard inboard/outboard speedboat, the other is one of those Everglades air boats. The two boats often drag race on the calm lake, and it always ends in a dead heat.

The guy with the Everglades air boat offers to drag race the speedboat, with $1000 riding on the outcome-- and if the race ends in a tie, the speedboat driver wins. The only condition the air boat guy mentions is that, rather than race on the lake, they'll race on a fast-flowing nearby river, heading upstream.

Should the speedboat driver agree to the race?

 

There are some interesting ideas coming out, not necessarily correct but still interesting. I will add aircraft type does not matter and flight info is not needed. What will happen is true for all aircraft, assuming the aircraft is flight worthy.

So far, we have:
8 no
1 yes
and two noncommittal



Joe

 

Yes, because unbeknownst to either of them, the Everglades boat driver has a history of Tachycardia and about 45 seconds into the race he's going to go into full cardiac arrest and be dead before his body hits the floor of the boat. His Everglades boat will veer off to the right and come to a stop against the riverbank. The speedboat driver will win by a mile.

 

I don't know much about planes, but don't the wheels do something on take-off and landing like reverse or something? Or is that just landing?


I'm gonna say YES.

 

hahaha. That is a good question.

The plane definately takes off.

First off. If the plane moves because if its propellers or jet engine, it is impossible for the conveyor to keep up. What really affects the plane taking off. The plane is going to take off no matter what direction its landing gear is turning or how fast. A plane uses air to create horizontal movement. Air alone is what gets the plane going and keeps it in the air. The air is not moving in this example. If the plane were in a wind tunnel, the plane would remain stationary. But since only the conveyor is moving, the plane will take off just like any other day on any other runway. The plane will still take off at the same air speed no matter what the ground is doing.

So in this example. Yes, the plane will take off. The only difference from this conveyor belt runway and a normal runway is that the wheels on the plane will be turning twice as fast to keep up with the conveyor belt, but the plane will do the same air speed as normal.


And the boat question Phil. The guy in the speedboat is in trouble if he takes the bet. Airboat wins.

 

Rehashing it for a while I am 100% convinced that it will take off.

Once I got over the thrust vs momentum pardox and got my head out of my butt it became clear.

That was a good one Wookie!


Edited to add:
Lightning R got it while I was typing.

 

Now for this one...

I would not do it in my boat.

Once both boats are on plane the air boat displaces less water.
Which means that the current of the river will be applying alot more pressure on the power boat. Also a standard I/O prop can only push so much water. The current will be taking forward thrust away from the prop. (Example; a 14/17p prop means that it is 14" in diameter and will move forward 17" for every rotation through a solid object. "IE jello".) So it will be moving throu the same amount of water but not gaining ground speed.

The Air boat basically glides across the top of the water and is pushed by air. He will achive the same land speed from his prop and only slightly be slowed by the drag of teh current.

 

the boat and plane question are of the basic question. The rules of the answers apply to both.

 

The AV-8B could take off- with the wheels doing 1 MPH, or 300 MPH. But, with no forward velocity, the wings would develop no lift- and therefore, would not fly...

Many planes have to do at least 180 kts to get off the ground- except maybe those little prop cessnas, and ultralights- where it's all about thrust to weight ratio...

 

With the boat you have two different scenarios and two totally different methods of propulsion. The air boats propulsion will not be affected by the current, only by the drag created on the hull.
An I/O or an Outboard either one that pushes water to propel will be affected by the amount of water pushing againts it.

The air boat will beable to achieve a higher ground speed while the slip of the Water Prop will alter it's ability to move forward.

Yes they will both have the same water speed. But the ground speed will be different.
Thats why a standard water pick up speedo on a baot is not accurate. Becasue it is powered by the force of the water as it runs under the boat. The faster the water move the more force applied. Not by the actual ground speed. There is often a 20 mph+ difference in the two. The faster the current the faster the water is moving across the bottum of the boat so the faster the speedo will show. But the boat is actually moving slower.

 

Correction....
It is not two different methods of propulsion, they are propelled using two different materials.
Speed Boat is powered by moving water.
Air Boat is powered by moving air.
Where ALL planes use air movement.

With the boat scenario you are drastically changing the charecteristics of the propulsion material of one object and not the other.

The speed boats water is already moving so he would have to push twice as much water to achieve the same ground speed. Where the air boats air would remain the same so he would only have to push the same amount of air to cover the same ground.

Now if there was a head wind exactly the same speed as the current of the river, then the variables would be equally altered and they would tie again.

 

you are forgetting where the forward velocity comes from.