A plane on a runway, how smart is r3vlimited?

[chucko]

The plane will NOT take off if it is facing opposite the direction the conveyor belt is moving. The plane WILL take off if it is facing the direction the conveyor belt is moving.

Assuming the plane is facing opposite the direction of the conveyor belt, and assuming the conveyor belt is capable of moving at an infinite speed, the wheels of the plane will NEVER move the plane forward relative to some initial position (inertial frame). The only way a plane can take off is with forward momentum relative to a fixed position and atmosphere (air). Remember, a plane needs no jets to take off, just needs to be moving faster than the air around it. Conveyor belt moves at an infinite speed to the left, the wheels of the plane move at an infinite speed to the right. The air around the plane does not move so the plane does not take off (jets have no impact on this problem).

That is the answer to your question folks!

[BENdashdash]

WTF.. There is no such thing as frictionless wheels. Is this question based on reality or science fiction?

science fiction. last i checked, theres no such thing as conveyor belts for airplanes that detect and instantly mirror wheel the wheel speed

[RobertK]

That GIF is wrong. The conveyer doesn't apply any force on the plane directly, just through the wheels, which can be assumed as frictionless.

WTF.. There is no such thing as frictionless wheels. Is this question based on reality or science fiction?

[DarkWing6]

I agree with Ben. It's not that the plane is driven by the wheels, it could be Jordan's car driven by a jet engine for all I care. The plane needs to move along the ground to create this force under the wings. If the belt is moving the opposite direction the same speed as the wheels (or the plane, same thing) it will not create this force. The jet engines propel the plane across the ground just like our cars are moved by our engines, drive line, etc. The wheels are relevant unless the plane takes off early and flys really low before actual "take off", which is not what this thread is even about.



Think about it this way. Put wings on your car and drive it really fast. It will take off if you were able to go fast enough. Once off the ground you would be screwed, but for the actual take off it would work. The jet engines or whatever is making the plane go are irrelevant. It is the force created under the wings.

[BENdashdash]

im winning votes, better come up with better propaganda :-p

[BENdashdash]

see, you're missing one important detail: gravity. the plane will be glued to the ground. if the plane is going 100 mph forwards, the belt will be spinning 100 mph backwards. because they will always go the same pace, they will be canceled out, thus creating a net movement of 0. i dont know where you got yout 200 mph number from. sure, the plane's wheels can roll at 200 mph, but the belt will be going just as fast. doesnt matter what kind of vehicle it is for that matter. the "plane" part is a distraction. its still being held to the belt by gravity, no jet is going to change that.

[Justin B]

Oh Ben, lol :)

First of all the plane is not powered like a car, it does not get the drive from its wheels, it gets it from a jet engine creating force through the air not through contact with the ground. The jets will push it through the air.

Here's how it will work really easy like, we'll assume there is no resistance at all on the wheels, even though there is, it is negligible and will not cause the plane to stay stationary.

We'll separate the accelerations of the plane and the roller underneath to make it really simple.

1) Conveyor belt starts turning backwards at 100mph, since the plane has no drag on the wheels it stays stationary. The planes wheels however, are spinning at 100mph to keep the plane stationary. As far as they are concerned, the plane is traveling at 100mph.

2) Plane accelerates to 100mph instantly (for sake of the example), now, the plane is going fast enough to lift off, and the wheels are now going at 200mph to keep up with the plane, and the belt spinning backwards. Really though as far as airflow over the wings though is concerned, and in reality, the plane is only traveling 100mph.

Now, the questions requirements are satisfied, the conveyor belt is going as fast as the plane is, and the plane may lift off.

If you want to get technical and throw in wheel drag in there, take two examples-

1) The plane on a normal runway will have a certain amount of drag from its wheel to reach and maintain 100mph. Great.

2) The plane on the conveyor belt will need to use a little bit more thrust, andwill need to accelerate for a slightly longer period of time to reach 100mph ground speed. Ground speed, meaning speed of things to the side of the belt, the rest of the world. The wheels are spinning at 200mph, its a miniscule amount of extra drag, but its there, but possible to overcome.



I'm going to dinner. I'll be right back :) At least I am getting in a lot of typing.

[BENdashdash]

im still waiting for you to prove me wrong :)

[Justin B]

<Merlin> Do you remenber the pic of the kid with down syndrom running that people were using in there arguments
<kfunk> some people get locked into a dumb answer, and refuse to change their mind, or else theyd be admitting they're a fool
<Justin> yeah I do sam
<Merlin> Kfunk you hit it on the head
<Merlin> thats what your fighting J
<Justin> rofl
<Justin> i am going to post that in the thread
<Justin> thank you

[BENdashdash]

Justin, would a car move forward?

[dirty30]

now take that same fan and mount it on a dock and aim it at the sail.....

[BENdashdash]

Ben, it will not.

ya huh!

[BENdashdash]

what if you take a sailboat, then put a huge fan on the boat and aim it at the sail... then turn it on.... will it move the boat?

i think even the "smarties" can agree with me on this one. no.

[Justin B]

Ben, it will not. I'll just leave it at that this time around. I am really tempted to write the whole thing over again, but I wont even mention why it'll move.

[BENdashdash]

justin, at first i was with you on this one. you know, trying to find an explanation to counter the obvious. turns out, there is no such thing. belt will match the speed of the plane, and thats all there is to it.