You are right here. The cart is pulling by apllying force to the ground or belt. But in the original problem the plane is applying force to the air around it not the belt. IT WILL FLYKEVINS said:This theory doesn't work because you have a source outside the "Working System" relative to the movement of the plane and belt. Put that cart on the belt with a chain to the plane THEN you have the cart "inside" the Working System and the plane will NOT fly.
ks
Physics question.. can you figure it out?
- Thread starter TType84
- Start date
Welcome!
By registering with us, you'll be able to discuss, share and private message with other members of our community.
BLACK6PACK said:
The airplane's wheels can move at 1,000 miles an hour... it won't matter, they don't create lift, wind over the wings create lift.
If all that is needed to make an airplane fly/liftoff is to spin the wheels at 140mph what are the wings for than?
I still say as long as the airplane is moving the opposite speed and direction of the belt (original condition) it has zero airflow over the wings and zero lift.
Pete
No it won't.jpratt said:
Planes fly because of the change in distance relative to a single point on the ground because the air is relative to this same point. If this point never changes (plane speed in X direction = belt speed in -X direction) then the point relative to the wind is still the same so it won't fly.
ks
I can come up with another couple of slants to this problem, but I don't think I'll open that can of worms 
I don't want to upset you guys who think this is serious
Without further clarificaton as to terms of what speed is to the involved parts of the problem, logical cases can be made for both sides.
I think almost every example you guys gave had merit. Opposing sides are just looking at it from a different perspective.
I don't want to upset you guys who think this is serious
Without further clarificaton as to terms of what speed is to the involved parts of the problem, logical cases can be made for both sides.
I think almost every example you guys gave had merit. Opposing sides are just looking at it from a different perspective.
The wrong perspective.1ARUNM said:
Kevins, the plane pushes against air. Do you understand that? If yes then how is the engine pushing air if it is not movining relation to the ground? Did you watch any of those videos earlier? The skateboard with the fan should prove it.
I think everbody should end their statements with
IT WILL Fly or it will not fly
IT WILL FLY
83hurstguy
Member
- Joined
- Sep 18, 2005
- Messages
- 566
to really prove the other side saying it wont fly wrong... take this for example.
Let's say the conveyor belt is actually keeping the plane from moving relative to the ground. Then the ground speed AND the airspeed of the plane is ZERO. This would mean that the conveyor would stop moving b/c all recorded speeds of the airplane are zero (since conveyor has to match airplane speed).
hmmm... the damn thing flies. period.
haha, I see V6 Beast just said pretty much the same thing in the time it took me to type this.
Let's say the conveyor belt is actually keeping the plane from moving relative to the ground. Then the ground speed AND the airspeed of the plane is ZERO. This would mean that the conveyor would stop moving b/c all recorded speeds of the airplane are zero (since conveyor has to match airplane speed).
hmmm... the damn thing flies. period.
haha, I see V6 Beast just said pretty much the same thing in the time it took me to type this.
turbot2496
New Member
- Joined
- Mar 16, 2003
- Messages
- 1,346
AGGHHHHHHH!!!!!!! and Kevins I know you are a smart cat so I can't figure out why the heck this is stumping you. THE WHEELS ON THE PLANE ARE FREE WHEELING.... THE PLANE WILL MOVE FOWARD ON THE CONVEYOR THUS MOVING THE AIR OVER THE WINGS... THE CONVEYOR BELT CAN'T HOLD THE FRICKIN PLANE BACK IF THE WHEELS ARE FREE SPINNING!!!!!!!!!! THE PLANE IS NOT PROPELLED FORWARD BY ITS WHEELS. THE SPEED OF THE FRICKIN CONVEYOR BELT DOESN'T EVEN MAKE A DIFFERENCE.
Whew.... ok I fell better now :biggrin:
turbot2496 said:
For the airplane to move forward on the conveyor violates the original condition:
"that tracks the plane speed and tunes the speed of the conveyer to be exactly the same "
IF YOU ONLY NEED A CONVEYOR BELT TO TAKE-OFF WHY DON'T AIRCRAFT CARRIERS USE THEM? WHY WOULDN'T ALL AIRPORTS USE THEM IT WOULD SAVE A LOT OF SPACE ESPECIALLY IN CHICAGO/O'HARE
IT WON'T FLY
Pete
1ARUNM said:Kevins is talking about speed in relation to the conveyor belt and you aren't, you are both right in your own way, that's why it's confusing
It's not confusing once you realize that Kevins is wrong. The problem states "The plane moves in one direction, while the conveyer moves in the opposite direction..."
Either the plane moves or it doesn't. If it doesn't move then the belt never moves because it only moves at a speed equal to the plane but in opposite direction. If the plane isn't moving forward then the conveyer doesn't move. It doesn't say the conveyer moves as fast as the planes wheels are spinning or as fast as the planes speedometer reads but in opposite direction. It moves at the same speed the plane itself moves but in opposite direction.
Where Kevin and others go wrong is they think of it like a car where the movement is due to contact with the ground. A car driving at an indicated 60 mph on a conveyer that was moving 60 mph in the opposite direction would just sit there in the same place. Just like running on a treadmill. FOr a car to move forward at 60 mph on a conveyer moving at 60 in opposite direction, it's wheels would have to spin twice as fast and it's speedometer would have to read 120 but it would still only be moving at 60.
But in this scenario the runway moves under the plane at the exact same speed the plane is moving forward. So if the plane is movng forward at 200 mph then the conveyer runway is moving in the opposite direction at 200 mph. If they plane had a speedometer attached to it's wheels, it would indicate a speed of 400 mph but it would actually only be moving at 200 mph. This is where "you would have to go faster than the conveyer thinking comes from" Yes the indicted speed would have to be faster than the conveyer but the actual speed would not.
The plane would move forward at 200 mph the conveyer would move in the opposite direction at 200 the speedo on the wheels would read 400 mph and the plane would take off.
How can it be any more clear?
turbot2496
New Member
- Joined
- Mar 16, 2003
- Messages
- 1,346
NO IT... uhh excuse me ..... no it doesn't.. nowhere in the original problem does it state the the plane can't move forward on the conveyor. The speed of the conveyor makes no difference. It can't keep the plane from moving foward because the wheels on the plane are free spinning.......
BLACK6PACK
1 sec reaction King
- Joined
- May 24, 2001
- Messages
- 4,849
87 Pete said:
You're right, the planes wheel speed doesn't make a difference. Where does the plane get its mph reading? It gets it from air moving through the air speed indicator thingy. So if the plane is moving 70mph it is moving forward at 70mph, the conveyer is moving at 70 in the opposite direction in essence the closing speed between the two 140 mph. Take the conveyer out of the equation: the plane is moving at 70mph on a stationary runway, it has a 70mph take off speed, the plane takes off correct? Now put a conveyer under the plane going 70 mph in the opposite direction, it doesn't change anything other than the fact that the tires are moving twice as fast.
BLACK6PACK
1 sec reaction King
- Joined
- May 24, 2001
- Messages
- 4,849
Put a grand national and the plane that takes off at 70mph (with and identical GN motor in it) on the conveyer. Start moving the conveyer, the plane has to give a little throttle to overcome the drag from the bearings in the wheels, the GN has to match the speed of the conveyer mph per mph to stay stationary correct? So now the conveyer is moving at 70mph, the gn is running at 2200 rpm @ 70mph and is stationary, lets say the plane can cruise in the air at 70mph @ 2200 rpm. The plane is running @ 2200 rpm but due to its thrust and the fact that it doesn't matter what the wheels are spinning at it moves forward at 70mph and takes off. Planes don't have gears. The drivetrain has no connection to the ground. So, the GN stays stationary with its wheels spinning at 70mph, the plane having no connection to the ground other than free spinning wheels moves forward and takes off.
turbot2496 said:
I guess it depends on your definition of "airplane's speed" in the original condition:
"This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in opposite direction)."
Same speed to me means that it cannot move forward relative to the ground. IF they have different speeds i.e. treadmill at -100 mph and airplane +300 mph relative to the ground, yes it would move forward along the treadmill and takeoff.... But to my interpretation it violates the definition of "same".
Pete
The example I gave does not have the cart on the belt also, the cart pulling the plane is on its own surface. The plane has to follow. Remember the engines provide the thrust. No matter how fast the belt moves below the engines the engines will move forward when they put out thrust. It just so happens the plane is attached to the engines and has to follow them down the runway. Can you picture that? the engines will accelerate up to take off speed no matter what the conveyer belt does. The plane will follow the engines as it is attached
87 Pete said:
Well if it's not moving forward relative to the ground then the conveyer isn't moving.
Think of it like this. When you use your line lock, lock your front tires, do a burnout and your speedo says 100 mph is there anyway that you could say the car is going 100 mph? Relative to anything?
No of course not.. you know that car is moving no where. Well that is what you non-flyers are trying to say. A plane sitting there spinning it wheels at 100 mph would cause that the conveyer is going to move at 100 in opposite direction. Now that is what violates the definition of the same.
The conveyer moves at the same speed as the plane moves. Sitting in the same spot is not moving. The plane and the conveyer have to use the same point of reference to determine their speed. You can not use the conveyer for the planes point of refererance and the ground for the conveyers.
I guess I was able to make it more clear afterall....
KEVINS said:I stick by my 6 years of Engineering education and countless hours in physics and dynamics classes that say that the plane will not fly.
Ok smarties,
ks
What school did this engineering education come from?
We have runways because it won't sit there on the conveyer. Duh. That's the whole point! It moves forward on the belt just like it would on water, just like it would on snow, just like it would a perfect surface that has no firction where a car would sit and spin for infinity.
Similar threads
