will it take off?

[Paddy]

The trick in this "trick question" is the wording of .....Matching the speed on the airplane.

Camp 1 Feels the speed is related to air plane wheel speed
Camp 2 Feels the speed is related to air plane body speed

In the Camp 1 result, no forward motion, no fly
In the camp 2 result, forward motion is equal to conveyor speed, will fly with wheels spinning double.

Some have have stated you can't use a car or a runner as a comparrison because to power source is transferred via air vs. through traction of feet/wheels. I dissagree, the trick is the same. If you are in camp 1, car tires spin at the same rate as the convayor and won't move relitive to the ground. Camp 2 will states the car and convayor will be traveling at 25 mi/hr in oposite directions when speedometer shows 50 mi/hr.

It's all in how you understood the problem. I don't think there would be any debate if we all understood the speed referenced in the problem was air plane speed, not tire rotational speed.

 

[Egon]

Lardy, Lardy Me's Bye's;

Have you realized the potential launching system the aircraft carriers have missed out on! They still use an antiquated steam system do they not.

Think of airports and how runways could be shortened for takeoff!

" Its time for someone to make their fortune " Go patend the system
Aircraft crashing on takeoff occurences should surely go down

 

[MossRoad]

Lardy, Lardy Me's Bye's;

Have you realized the potential launching system the aircraft carriers have missed out on! They still use an antiquated steam system do they not.

Think of airports and how runways could be shortened for takeoff!

" Its time for someone to make their fortune " Go patend the system
Aircraft crashing on takeoff occurences should surely go down

Now that would be a fun flight to Vegas!!

 

[jwnge]

Ok. plane is on conveyer, plane is tied to a winch, conveyer moves foward, planes wheels turn foward as fast as conveyer spins opposite. plane sits still, turn winch on, wheels on plane spin faster, plane moves foward as winch pulls, pretend winch is engine powered prop..daaaaaaa, pretend plane is Cub, when winch reaches 50 mph, plane takes off. if winch is not released Cub is in trouble, if pretending winch is engine with prop, Cub is flying. that is my story and I'm sticking to it.. John

 

[RobJ]

Anyone ever see a float plane take off going up river?

So the answer is yes the plane will take off.

A river is not matching the planes speed. Ever see a runner run off the front of a treadmill that's matching his speed? nope. Only way is if the runner speeds up and the treadmill does not.

I've only read 2 pages but it's clear the plane will NOT take off. What is a plane before it becomes airborn? It;s a car, a bus, it's a train. The wheels allow it to move across the ground to gain airspeed. If the belt matches it's intended speed, it'll never move anywhere. People said a plane uses a prop not the wheels to move. Well duh, but so what. The wheels must spin and allow the plane to move forward. If I were to push a car by hand (not powered by wheel) on the same conveyer the sane thing would happen. Nothing, the car would not go forward because the conveyer is matching the speed of the wheels. And for those that say the belt will cause enough wind...well that's just silly.

Funny how some who make the case for flight, actually make a case for no flight.

 

[NewToy]

A river is not matching the planes speed. Ever see a runner run off the front of a treadmill that's matching his speed? nope. Only way is if the runner speeds up and the treadmill does not.

I've only read 2 pages but it's clear the plane will NOT take off. What is a plane before it becomes airborn? It;s a car, a bus, it's a train. The wheels allow it to move across the ground to gain airspeed. If the belt matches it's intended speed, it'll never move anywhere. People said a plane uses a prop not the wheels to move. Well duh, but so what. The wheels must spin and allow the plane to move forward. If I were to push a car by hand (not powered by wheel) on the same conveyer the sane thing would happen. Nothing, the car would not go forward because the conveyer is matching the speed of the wheels. And for those that say the belt will cause enough wind...well that's just silly.

Funny how some who make the case for flight, actually make a case for no flight.

Not at all like a wheel driven conveyance. The prop, jet, turbo prop, etc is driving the plane not the wheels. Wheels will spin freely at 2x the speed of the belt as the plane LIFTS OFF!! Go back and look at a few of the links for a better explanation. Conveyor has nothing to do with it other than adding a bit of resistance from the friction inherent in bearings and the tires rolling resistance. Keep thinking about it or look at the posted links, it will come to you. No "Duh" about it, the plane flies. Nothing to do with the belt generating wind either.

 

[rutwad]

ASSUMING THIS IS NOT A TRICK QUESTION, BUT TRULY A QUESTION OF PHYSICS, THEN

1> For those that say "It will not fly". Under normal circumstances, no conveyer, what propels a plane?

 

[755inNY]

A river is not matching the planes speed. Ever see a runner run off the front of a treadmill that's matching his speed? nope. Only way is if the runner speeds up and the treadmill does not.

I've only read 2 pages but it's clear the plane will NOT take off. What is a plane before it becomes airborn? It;s a car, a bus, it's a train. The wheels allow it to move across the ground to gain airspeed. If the belt matches it's intended speed, it'll never move anywhere. People said a plane uses a prop not the wheels to move. Well duh, but so what. The wheels must spin and allow the plane to move forward. If I were to push a car by hand (not powered by wheel) on the same conveyer the sane thing would happen. Nothing, the car would not go forward because the conveyer is matching the speed of the wheels. And for those that say the belt will cause enough wind...well that's just silly.

Funny how some who make the case for flight, actually make a case for no flight.

Please read the problem again. The conveyor is not matching the speed of the wheels. It is matching the speed of the plane.

Let's turn the problem around. Plane is sitting on the conveyor with its engine idling. Let's say the take-off speed for the plane is 50 mph. Now instead of the conveyor matching the speed of the plane the goal is for the plane to stay in one place as the conveyor accelerates to 50 mph. As the conveyor starts to move the pilot adds just enough power to keep the plane from moving backwards on the moving conveyor but not enough to move forward. This will take very little power, a few hundred rpms, because the wheels will spin freely on their bearings. Once the conveyor gets up to 50 mph and with the plane still in the same place, the pilot adds full power. The plane will accelerate down the conveyor with the wheels spinning faster and faster to take up the difference between the conveyor speed and plane speed. When the plane reaches 50 mph, equal to the speed of the conveyor going in the opposite direction, it takes off. The wheels are spinning at 100 mph.

Again, the problem states the conveyor matches the speed of the plane not the wheels. If the conveyor was matching the speed of the wheels then, of course, there would be no forward movement of the plane. But that is not the way the problem was stated.

 

[RayH]

Please read the problem again. The conveyor is not matching the speed of the wheels. It is matching the speed of the plane.

Let's turn the problem around. Plane is sitting on the conveyor with its engine idling. Let's say the take-off speed for the plane is 50 mph. Now instead of the conveyor matching the speed of the plane the goal is for the plane to stay in one place as the conveyor accelerates to 50 mph. As the conveyor starts to move the pilot adds just enough power to keep the plane from moving backwards on the moving conveyor but not enough to move forward. This will take very little power, a few hundred rpms, because the wheels will spin freely on their bearings. Once the conveyor gets up to 50 mph and with the plane still in the same place, the pilot adds full power. The plane will accelerate down the conveyor with the wheels spinning faster and faster to take up the difference between the conveyor speed and plane speed. When the plane reaches 50 mph, equal to the speed of the conveyor going in the opposite direction, it takes off. The wheels are spinning at 100 mph.

Again, the problem states the conveyor matches the speed of the plane not the wheels. If the conveyor was matching the speed of the wheels then, of course, there would be no forward movement of the plane. But that is not the way the problem was stated.

755inNY,
You were right on the mark until that last paragraph.
The conveyor could match any speed, that of the airframe or that of the wheels, the plane will still move forward and take off because theres nothing holding it back. The conveyor could be going 500MPH in the wrong direction and the only effect will be on the wheel bearings and tires.
Its really that simple, NOTHING IS HOLDING IT BACK. the wheels are freewheeling on conveyor, as long as the prop is pulling it, it will move forward.

 

[shaley]

So, do you think if the conveyor was inclined to 15 deg the plane would fly? This would cause about 25% of the weight of the plane along with the conveyor to try to roll it backwards. I don't see how in one instance it can gain forward motion and then with a slight incline it can't.