A plane on a runway, how smart is r3vlimited?

[325iCabrio]

you are fucking stupid.

put a skateboard on a treadmill, put the speed to 2 mph, can you hold the skateboard in a stationary position with the wheels rolling backward?

yes.

put the speed to 5mph

can you still hold it?

yes

What I have just demonstrated is equivalent to the jet engine overcoming the friction of the wheels, you hand is acting like the jet engine.

Now push the skateboard forward, does the skateboard not move forward even with the wheels spinning backwards?

yes it does.

your hand is no different than a jet engine.

you could put the treadmill to 1000mph and your hand would still be able to push it forward, just like the jet engine. It could still easily get up to speed and take off.

Fine, you guys are right, and nobody else can have a differing opinion on a non-existant situaiton. I think next time we should just put a question as a locked sticky, because obviously nobody wants to discuss the question. They just want to be fucking right.

[ToplessE30]

Newton!!!

[Jand3rson]

Seriously, this thread needs to die in a fire. 355 posts is just fucktarded.

[RCWells]

Sorry, but one thread of idiocy is more than enough at one time.

[Fidhle007]

I've Been Censored By The R3v Man, Dammit!!!!!!!!!!!!!!!!

[erik325i]

Eric325i, quit arguing with these retards. If they haven't got it by now, they obviously have no understanding of the physics involved and are too stubborn to read and think about it a little.

Yeah, I tried. I convinced some people, but if other's haven't got it by now, it's no use telling them once more...

I'm done with this thread (again). The correct answer is on the first page (written by me).

-Erik

[ptownTSI]

if you can't figure out how a damn jet engine works and that the wheels have nothing to do with it, you are dee dee dee.

[joshh]

I think it's time for this thread to get the cut. The insults are making my skin flake....

[ptownTSI]

you are fucking stupid.

put a skateboard on a treadmill, put the speed to 2 mph, can you hold the skateboard in a stationary position with the wheels rolling backward?

yes.

put the speed to 5mph

can you still hold it?

yes

What I have just demonstrated is equivalent to the jet engine overcoming the friction of the wheels, you hand is acting like the jet engine.

Now push the skateboard forward, does the skateboard not move forward even with the wheels spinning backwards?

yes it does.

your hand is no different than a jet engine.

you could put the treadmill to 1000mph and your hand would still be able to push it forward, just like the jet engine. It could still easily get up to speed and take off.

[Brew]

Eric325i, quit arguing with these retards. If they haven't got it by now, they obviously have no understanding of the physics involved and are too stubborn to read and think about it a little.

[325iCabrio]

If there was an equation built that allows infinity to be achieved by both objects and friction is no a factor then yes eventually the plane will fly.

Where I work our research is based on real world scenerios so giving answers based on fictional scenerios does not make sense to me. As a matter of fact it's kinda pointeless to argue theories on scenerios based in a non-existant universe.

Here's some more depth to the point I'm trying to get across.





If I had the coefficients I needed I could tell you if a particular plane could fly.

Basically you need an engine capable of putting out a lot of thrust and a larger set of wheels but eventually if you match everything up right the fucker will take off.

As of today I doubt anyone has every built a plane capable of surviving this scenerio short of a Harrier Jet. The tires and/or wheel bearing would most likely explode before achieving the ground speed nessesary for take off.

RitalinKid, that was the argument I was trying to make, but you did a much better job illustrating it. If the wheel are frictionless, then the plane will take off like it's on a normal runway. Hell, it'd probably take off faster, because if the wheels are frictionless in this world, the air is frictionless too, and it won't take as much thrust to lift off.

However, since wheels do have friction, the plane would need a longer runway to take off to counteract the added friction of the conveyor belt opposing the plane and wheels. I don't know how much friction it'd cause, so I can't tell you whether you'd need a much longer runway or only one with a few extra feet.

This is a cool question. At first I thought it'd stay in one place; then I thought it would take off fine; and then I thought it'd need more space because of the added friction. At least it makes you think! :D

[AdironRider]

I say it again. The wheels do nothing in the equation. They just spin there. They dont have any effect.

Think how a plane on pontoons takes off from a lake. The engines push the plane forward against air resistance, it has no effect whatsoever what medium or how the runway is acting. You can take off a river going upstream no problem, it doesnt effect the planes speed for takeoff either.

[BimmerToad]

wow, I leave for an extended weekend and come back to Eng 101 on r3v

The plane will take off.

Make simplfying assumptions like that the wheels spin without friction, without sticking or slipping visualize it.

Just think of the Jackass stunt with the rockets strapped to a pair of skates

[Fidhle007]

You are right, sort of. I said the car was TRAVELING at 60, not that the speedo was reading 60. And hence I think I illustrate where the discrepancy in the answers to the original question lie. In my scenario, if the the speed of the car were being calculated but a police officer with a laser gun the vehicles forward velocity would be 60 mph but the speedo would read 120.

So lets apply this to the plane scenario and fill in some of the details a bit: The plane is a Piper Cub and the conveyor is moving at 70 mph. If the Cub's foward speed is also 70 mph then the plane will certainly lift off, despite the fact that the wheel speed is somewhere's around 140 mph. I picked a Piper because their takeoff speed is not much over 60 mph and they only need a few hundred feet of runway. Keep everything small and the liftoff argument makes sense I think.

[RobertK]

I honestly think it's all in your interpretation of the original question. When I first read it I thought no, the plane could not take off it the belt were somehow able to keep the plane stationary, but I suppose in the real world (if we discount wheel speed and go entirely with plane speed,) sure, the plane will take off. If it were a car, you'd be measuring wheel speed but because it's a plane, you're measuring forward motion.

I ask you guys this though:

If a CAR were to be traveling at 60 mph, on a conveyor belt that's also moving at 60 mph in the OPPOSITE direction, will the car ever move forward? And if it would and the conveyor belt was 30 miles long, how long would it take before it hit solid ground? And if it ever did hit solid ground, how fast would it me traveling?

I'm tempted to post this as another thread just to see what peoples answers will be.

~Brendan

Since the wheel is powered the car would stand still at 0mph. At 61mph the car would be moving 1 mph. After it drops off the conveyor engine would die because it would be the equivlant of doing 1mph in 4th gear. In a car's transmission inertia is it's friend. We've already been over this.