Plane on a conveyor belt

[Guest]

thrash;199282 wrote:
I beleive these statements are both false. You are in effect asserting that fluid dynamics does not exist.

Have you ever been to the lake before? Stand on the dock, hold on to a boat via a peice of rope. Are you saying the rope tension never changes because of waves or currents in the water? Are you saying that no matter what the water is doing, the tension on that rope (and via extension, the force you apply) never changes? I don't think you are...

An external force (you, attached to the land), trying to hold an object still in a moving fluid (air and water are both fluids) will need to vary your supplying force to counteract changes in the force the fluid is applying to the object.

Ok...I may be off in my assessment here, I was merely going off what was presented to me on phys.org and some pilot forum I was on. The conclusion, on both, was that once the airboat/seaplane were moving, the waters direction & speed had a very minimal affect on whether they could take off (or travel in opposite directions in the case of the airboat which is not designed for flying) or not.

I see. In that case, next time someone is doing a 1000hp dyno run, instead of using multiple ratchet straps, why don't you just hold onto the car yourself?
**
This is a bit different though, in this case the car is pushing the rollers, not vice-versa, so therefore the car is generating the forward motion. See my analogy of a toy car on a belt sander earlier in this thread for reasons why I think I can hold a car from crushing me on a conveyor belt (assuming the car is stationary and in neutral at the start of the test and I don't have to overcome momentum as well)**

If you were to replace the "you" in that picture with a spring, the spring will slowly compress as the speed increases, because we are talking about an imperfect system with non-zero mechanical losses.

This is incorrect. If for no other reason than there is no ground-launched lift-effect aircraft with a takeoff speed of 300mph. You won't see a plane making 300mph on land during a takeoff run

I said belt speed, not plane speed. The plane (if its a 747 for example) will take off when it achieves 180mph relative to the ground.

In any case, suppose the landing gear is a square block. The plane will certainly not take off.

If the square block is extremely slippery, it certainly could.

Suppose that the landing gear is a frictionless rolling assembly. The plane will definitely take off.

Assume it has its normal friction and it will as well

Reality is somewhere inbetween. That's why you can't make this an absolute statement.

**I'm pretty sure that just about everyone would agree that the scenario at hand assumes that the aircraft in this riddle is in normal operating condition. Throwing oddball scenarios out there certainly make it possible for it not to take off. Why not say something like "well, what if the plane has 3 engines pushing it forward and 9 engines pushing it backwards and the 3 forward engines only produce 10000 lbs of thrust each and the 9 backwards engines produce 100000000000 lbs of thrust each...can the plane take off?" Of course not. **

I'm not sure what physical property of aircraft you are referring to such that you can claim that no matter what, given enough time and distance, the plane will accelerate enough to take off.

So long as the aircraft can generate enough thrust, in enough space, with enough fuel, to overcome the momentum generated by the plane moving backwards at 300mph, the plane will take off. Every time.

Again...clarified.

As for the original question, the plane will always take off under normal conditions/parameters of the question. There is absolutely nothing that the BELT itself can do to prevent this if it follows rules of the question. The only thing that can prevent the plane from taking off is the plane itself.

[Guest]

JN210;199287 wrote:
I think someone should actually try this at home....with an RC gas plane and somekind of belt....just a thought.

glad you asked...

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

[Guest]

JN210;199280 wrote:
woah...easy, I just asked him if it would take off and he simply gave me an answer.

And I think he is retarded. Have him read the whole thread, and seriously think about what he said. If he still thinks that way, he should be fired.

[Guest]

HandoEX;199290 wrote:
tjamz and thrash have hereby gone completely crazy.

lol, I think only he and I actually read each others threads.

[HandoEX]

tjamz;199295 wrote:
lol, I think only he and I actually read each others threads.

Nope, Brian reads them and then gives me cliffs:)

[Guest]

In that case, brian is crazier than both thrash and I.

[Guest]

I didn't get to 7059 posts on this forum by sitting around and not responding...

[JN210]

^no kiddin? I think I will see if my teacher has anything more to say on this subject, I will show him what you all think and have him read up a bit on this, then I will see what he has to say.

[bubba]

HandoEX;199296 wrote:
Nope, Brian reads them and then gives me cliffs:)

Didnt we agree at Bdubs that every post over a certain length needs to have cliff notes...some of us dont have the time or attention span to read some of this, lol....

[JN210]

what would the cliff note be for this thread now? "so far, everyone is trying to prove their little points"

[DaveH]

Thrash's argument theoretically holds up, but if you are talking about any modern airplane then it will not hold up. The friction from the landing gear rolling on a conveyor belt is insignificant. Thrash's analogy about holding the car with your arms is a good one, but there is a significant difference in strength between a human's arms and a jet engine.

Maybe Orville and Wilbur's plane may have had a tough time taking off on the conveyor.

[DaveH]

JN210;199302 wrote:
what would the cliff note be for this thread now? "so far, everyone is trying to prove their little points"

Smart people are try to explain to Retards that a plane on a conveyor belt will still take off.

:icon_santa:

[JN210]

^lol, good one.

[Used]

Is it a propeller airplane or a jet airplane.. It might have been stated but im not going to go back and read the rest of that..

[Guest]

for the most part, it doesn't matter if it is a prop/jet/rocket plane.

[JN210]

The wheels can move as fast as possible but the plane will go NO WHERE without AIR lift which is not achieved by sitting still.

[KA-T_240]

if the plane is moving, air will be flowing across the wings. it doesnt matter how fast/slow the conveyor or the wheels on the plane are moving.

[Guest]

JN210;199320 wrote:
The wheels can move as fast as possible but the plane will go NO WHERE without AIR lift which is not achieved by sitting still.

GAAAAAAAAAAAAAAAHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!

let me spell this out

plane moves ----------------------------------------> at 180mph (relative to ground)

conveyor moves <------------------------------------------ at 180mph (relative to ground)

wheels spin clockwise at the same rate they would if the plane were traveling 360mph (180mph rotation from each force being applied to them).

Plane DOES NOT SIT STILL, the engines are pushing it ----> at 180mph. The plane is moving 180mph (I use 180mph as that is the speed a 747 needs for takeoff) vs the stationary ground.

There is absolutely no way (with a properly functioning plane) that the conveyor can prevent the plane from rolling forward along its surface. The conveyor does not/can not keep the plane from moving forward. If it can, I challenge you and your teacher to show me the physics on how it can be held in place (aside from anchoring the plane to the ground)

Basically, you are confusing speed with force. The conveyor does not produce enough force to hold the plane stationary. Period.

Please tell me your physics teacher did not tell you to type that response either. If so, it explains a lot about why kids are dumber than ever before (and if so, yes that was a direct shot at you and your physics teacher...if not, it was just a shot at you.)

[Guest]

JN210;199320 wrote:
The wheels can move as fast as possible but the plane will go NO WHERE without AIR lift which is not achieved by sitting still.

You are correct, a stationary plane will not take off. This plane is not stationary and the conveyor has no means to make it remain stationary. (civil answer/cliff notes for my previous post)

[SmitEvo]

I dont think you can call anyone an idiot in this situation considerent everywhere you look on this subject you can find plausable reasoning on each side such as the bernoulli effect not taking place or the wheels being irrelevant. I think it will take off unless the brakes are applied