conveyor belt and plane answered at last ??

[joe-90]

FFS Uri. Newton's law tells you the engines will push and they do. Forget the wheels and belt the engines have a contract with the atmosphere - they don't drive the wheels. The wheels simply turn at twice the speed they would normally turn at on a standard runway.

 

[UriBentMySpoon]

FFS Uri. Newton's law tells you the engines will push and they do. Forget the wheels and belt the engines have a contract with the atmosphere - they don't drive the wheels. The wheels simply turn at twice the speed they would normally turn at on a standard runway.

The engines push, yes, the plane rolls on its wheels, yes, on a static runway the plane would travel forward yes. But if the conveyor belt moves at an equal/opposite way, the thrust is in effect cancelled out. The thrust has to generate a speed faster than the conveyor belt for it to be able to move off.

If the plane has engine off, but the conveyor belt moves backwards, the plane moves backwards. If the thrust creates a greater speed than the belt is moving then the plane moves forward. if the speed forward is equal to the speed backwards then from the observer away from the conveyor belt the plane is still.

From an observers point of view, form the conveyor belt or from the plane looking at the conveyor belt, the plane is moving.

However with equal speed moving forwards and backwards, the plane is not travelling through the air, so no lift is generated.

Newtons Third Law is still in effect, nothing is contravened.

 

[doitall]

The forward thrust projects the plane along the ground. The ground in this case is the conveyor belt. The plane moves at one mph forwards, the belt 1 mph backwards. forward motion to the observer standing away from the belt is effectively cancelled out. In response to Newtons Law, the plane is moving along the conveyor belt.

Assuming no winds the plane is not moving through the air, no pressure created, no lift.

That is correct Uri, if you mark a 10mile finish line, and run the belt at 10mph, start the engine and tick over so the plane stays in the same spot.

After 1hout the plane will dross the finish line without moving an inch or 28mm for the pedantic.

 

[joe-90]

The plane travels at 100mph - belt travels at 100mph. Wheels turn at 200mph - but so what? Who cares how fast the wheels turn? Plane reaches 180mph - so does belt. Wheels turn at 360mph and the plane takes off as normal. Gedditt yet?

 

[UriBentMySpoon]

The plane travels at 100mph - belt travels at 100mph. Wheels turn at 200mph - but so what? Who cares how fast the wheels turn? Plane reaches 180mph - so does belt. Wheels turn at 360mph and the plane takes off as normal. Gedditt yet?

Whats generating the lift? No movement through the air to create the difference in air pressure? Geddit Yet?

 

[doitall]

Calm down Joe

We know the plane can take off at roughly 97.816mph but the wheel speed break the rules of the question so it cannot.

 

[joe-90]

The plane travels at 100mph - belt travels at 100mph. Wheels turn at 200mph - but so what? Who cares how fast the wheels turn? Plane reaches 180mph - so does belt. Wheels turn at 360mph and the plane takes off as normal. Gedditt yet?

Whats generating the lift? No movement through the air to create the difference in air pressure? Geddit Yet?

The engines travel through the air because Newton says they must - the plane is fastened to the engines. The plane MUST travel through the air, it simply has no choice. The wheels don't come into it.

 

[UriBentMySpoon]

The plane travels at 100mph - belt travels at 100mph. Wheels turn at 200mph - but so what? Who cares how fast the wheels turn? Plane reaches 180mph - so does belt. Wheels turn at 360mph and the plane takes off as normal. Gedditt yet?

Whats generating the lift? No movement through the air to create the difference in air pressure? Geddit Yet?

The engines travel through the air because Newton says they must - the plane is fastened to the engines. The plane MUST travel through the air, it simply has no choice. The wheels don't come into it.

The engines are not travelling through the air as there is no air movement. The wheels unfortunately do come into it because as long as they are rolling the plane is for all intents and purposes stationary. Whilst the planes forward motion is equalled by the reverse motion of the belt the plane is not travelling through the air any more than a plane stood still on a normal runway with the power off, no more than you or I stood still on the street.

 

[joe-90]

If it were a car with power through the wheels - then yes - but it isn't connected like a car - the engines have a contract with the air - not the road - where does the energy go when the engines deliver power? where does the thrust go?

 

[UriBentMySpoon]

The thrust is doing its job, it is pushing the plane forward. Along the conveyor belt. The belt is keeping the plane in the same place though as it equals the planes speed but in reverse. The plane is therefore not travelling thropugh the air as is required to generate lift.

 

[libby lou lou]

After 1hout the plane will dross the finish line without moving an inch or 28mm for the pedantic.

25.4mm

 

[joe-90]

The thrust is doing its job, it is pushing the plane forward. Along the conveyor belt. The belt is keeping the plane in the same place though as it equals the planes speed but in reverse. The plane is therefore not travelling thropugh the air as is required to generate lift.

No mate - the thrust is pushing it forward as Newton says it must - the wheels simply spin at twice their normal speed - the engines have a contract with the AIR and nothing can change that. The belt cannot drag the plane back through the AIR .

 

[doitall]

The engines travel through the air because Newton says they must - the plane is fastened to the engines. The plane MUST travel through the air, it simply has no choice. The wheels don't come into it.

Oh dear Joe.

After I get clearance I taxi to the end of the runway to a holding area, put the hand brake on and do a series of checks including full throttle.

Fortunately the plane doesn't shoot off in front of a Britannia that heading my way.

Now if I took the brakes off and the WHEELS started turning, I could move forward to the end of the runway at a nice gentle speed, give it 2400rpm and bomb down the tarmac at 85knots I'm in the air.

 

[UriBentMySpoon]

Imagine the plane cannot move at all, it is made of something indestructable, the engines are on full thrust. Where does the thrust go?

If the thrust cannot push the plane through the air, then the plane cannot create lift. If the air is still, the only air that is being moved is that which is displaced by the thrust. No air is travelling over the wings, no lift is created.

 

[joe-90]

If the thrust is on a test bed - where does the thrust energy go? Why are test beds massive concrete structures weighing a hundred tonnes or more?

But this plane isn't its it? It's on freely moving wheels. So tell me Uri - what is stopping the engines moving through the air?