Airplane physics question

+1


And a harrier flies either way so we’re done here right? Nowhere does the question specify a conventional prop driven airplane so there is no semantics argument to help you with this one. So you can feel cheated by the wording or cheated by the answer, but either the plane flies.

 

+1

 

This seems to be an argument around facts not in evidence. Some foolishness about a conveyor somehow counteracting the motion of something it has no connection with except through a free-spinning wheel.

Someone please explain how this could be possible.

Plane will fly whether the wheels spin or not.

 

The question states the conveyor is designed to match the speed of the WHEELS, not the PLANE. Which clearly implies the surface speed of the contact patch.

Therefore, if the wheel is moving FORWARD at 10 mph and the treadmill backward at 10mph. Then the WHEEL SPEEED is 20 mph....... oops

Or the wheel speed and treadmill speed are each 10mph, and the plane WILL NOT be moving forward.............. oops

Reread the original hypothectical question as it is written, not how it should be written in the real world of treadmills and airplanes.

 

OOPS
The original statement says nothing of rotational speed. It only talks about the speed of the wheels, and the fact that the treadmill goes in the opposit direction of rotation. No limit on rotational speed. Your assumtion. OOPS, No limit on forward speed of the plane again your assumption. Opps
You assumed that the rotational speed of the wheel and the backward spin of the treadmill are the limits. Problem says no such thing.
You can have a logical argument based on science in which case the plane will take off, or you can assume some magical
world where some magical drag force will develop and keep the plane from moving forward.
A lot of people made the wrong conclusion. Instead of accepting they got it wrong they argue that the question was poorly worded improperly defined, etc.

 

http://youtube.com/watch?v=-EopVDgSPAk

listen to the kid...lol

Antony

 

No it wont fly dont be stupid !

 

If man were meant to fly, Mr. Wynne -

God would have given him wings, Mr. Kidd...

And those two knew a thing or two about being light in their loafers!

 

Hey Victor, you look good in that Old Navy T-shirt!

 

Implies = Facts not in evidence.......

 

OMG

The problem is simple. Some are treating this as a logic problem and looking at the words, ignoring the physics. The title of the thread says PHYSICS question. Look at the physics and the problem is simple. Word problems are as much about being able to turn the words into physical reality as anything. If you can't do that, you fail. The plane flies.

I think what it really comes down to is that SOME people just can't ever admit that they are wrong.

 

BINGO

 

Sad but True.

 

Poking fun at me doesn't keep the plane from flying.
Once again using words when the facts don't agree with your position.

 

ROFLMAO. That kid on the youtube video could school some people here in physics.

 

What would be the first thing to come to your mind if someone asked you how fast any vehicles wheels were going?

 

Just to be clear I didn't say it in a mean-spirited way, and I respect your right post what you want.

 

The forward velocity of the wheel. Not the rotational velocity

 

Sorry Doc,

Wheel speed is commonly measured in revolutions per minute. This is all about rotation.

 

The speed of the belt is measured in feet per second or yards per minute or miles per hour etc. If the speed of the wheels is measured in RPM then the two can never be equal if there is any motion at all can they?
This is a problem about airplane PHYSICS. Not the grammatical structure of the question not the semantics or phrasing or spelling.
The question is about what provides the force on an airplane to make it move forward. If a plane was dependent on the wheels to keep it moving forward it would never be able to maintain flight.
The minority of people that still say the plane won't fly are now using rhetoric to try to prove the point. Put any real airplane on a treadmill fire it up let the treadmill go backward at whatever speed you want and the plane will fly 100% of the time.
If you want to use rhetoric to say the plan won't fly the go back to a philosophy class and argue about the mass of an infinite number of angles on the head of a pin. Because angles on a head of a pin are as realistic as a treadmill that will keep the plane from moving forward.

 

The wheel is driven by the belt in whatever direction and speed you wish. Surface speed of wheel and belt will be equal whether the plane moves or not. Wheel speed is typically expressed in RPM however surface feet per minute or miles per hour can be derived from this number.

You and I are in agreement that the naysayers are more focused on obfuscation than any understanding of how airplanes work.

 

The mechanics of forward motion with a rotating wheel are actually pretty complicated. The speed of a point on a wheel relative to the ground will vary as the wheel rotates. Paint a dot on the side of the wheel at its outer circumferance. Measure the forward speed of the dot at the top of the rotation and that spot will have a forward velocity that is twice the forward velocity of the axle of the wheel relative to the ground. At the bottom of the rotation that spot will have 0 velocity relative to the ground. It really depends on how you measure what the speed of the wheel would be.
I wonder where the linguistics purists are going to measure the wheel speed of the non flying plane. At the axle where according to them the speed will be 0 relative to the ground while the treadmill races by underneath, At the top of the rotation where the forward speed of a point on the wheel will be twice the backward speed of the treadmill or at the bottom of the rotation where the the contact patch will be going backwards at the same speed of the treadmill?
I do think that if you ask Joe Buba six pack or Mary Jane hot bod what the speed of the wheels under a semi going on the freeway they will say 70mph and not 1800rpm. It all goes back to the treadmill matching the forward speed of the wheel.

 

Just so you see that I understand physics, here is part of my first post in this thread:



"Short Answer: Of course the plane can take off.

This is a hypothetical question, like those used by physics professors to help with understanding the laws of physics. You don't need to take into account friction, wheel bearings, the rotation of the earth or the color of the flight attendants uniform.....not even the pilot's blood alchohol content is relevant in this scenario.

Jets take off because of engine thrust, they aren't wheel driven. Apply that thrust to the plane and it accelerates through the air mass. When it reaches flying speed it takes off. The plane doesn't care which way or how fast the wheels are spinning, or whether there is a conveyor belt under them."




I have been having my fun because of the wording of the original question. Now, re: your answer above, I think most people would not agree with you, and they would argue that "wheel speed" means just that: "wheel speed", not the velocity of what it is attached to. When Formula One engineers talk about wheel speed, they are NOT talking about the forward velocity of the wheel. You know why they have wheel speed monitors on all four wheels? So that they know what each wheel's speed is relative to the car, because they are often NOT the same as the cars speed. In fact without traction control this year, the rears will often be going 100 mph when the car is going 90mph.

 

It's not really complicated, and it is entirely predictable. It is just not linear.

 

crap. I voted yes before I read the whole thing. I should have voted no.