Airplane physics question

It is impossible. That's why I have been saying it is a conundrum.

 

If you assume that the conveyer is there to prevent forward motion, what is the purpose of the question? You have to decide whether or not the conveyer can prevent forward motion, not assume that it can.

Anyway, if the plane is sitting on a frictionless surface, it will most certainly move, and fly. A frictionless surface is what the wheels of an airplane are trying to produce. Obviously, that's not physically possible, so they do the next best thing, low friction surface.

 

Exactly, and exactly why you can't choose the rotation of the wheel as the speed that the conveyer matches. Which is exactly the choice the wording I gave eliminates.

 

Yup, you got it. Except enough thrust can be generated to lift off...that's how they get heavy rockets off the ground without wings. It's a matter of having the right amount of thrust and vectoring it in the right direction (downwards). It's also how VTOL aircraft work.

 

Art, here is another example of a conundrum:

A plane sits on the runway in Las Vegas.
The SAME plane at the exact SAME time is also sitting on the runway in Omaha.
Since the plane can only be in one city at a time, which city is it in?



Just like our original question, there is NO answer.

 

What he has got, is your wrong interpretation of the problem.

If this were the point of the question, nobody would disagree. It's beyond obvious that the plane cannot take off. That is not what the question is asking. It is asking if the plane can gain groundspeed on a treadmill. The answer is yes.

 

I am not assuming it can. Using basic physics principles, I am concluding that it does.

 

Oh MAN..........

 

I know what a conundrum is. The original question is not a conundrum because you can creat it. Instead of a treadmill, you can put a ski plane on a fast flowing water (you can control the flow) and then you fire it up. Keep the plane small and light, and you can do this experiment in real life. You can also use the skateboard and fan on a treadmill. I bet you that they can be made to stand still even if you apply more throttle to the engine or give more current to the fan, creating more thrust. All you have to do is increase the flow rate of the water or increase the speed of the treadmill.

 

No, you are using flawed physics to validate what you want to believe.

 

Right question and wrong answer.
How can the plane gain groundspeed if its wheelspeed is matched by the treadmill in the opposite direction at all times? How can the plane move forward without changing its wheel speed in relation to the treadmill speed? How can that change if the question says they always match?

It absolutely cannot. The groundspeed of the airplane stays zero.
Zero speed = zero airflow.
Zero airflow = zero lift.
Zero lift = no takeoff.

At least we agree on the question. Halfway there!

 

Art, you've been singlehandedly continuing this debate for the last 10 pages! I thought it would die out around page 25 and it's now at page 35 . (And yes it takes at least 2! )

 

Well, then, it should be easy for you to point out the flaw instead of just claiming that there is one somewhere.

 

Going for 100. Maybe the plane will take off then. Hah!

 

Because they're FREEROLLING WHEELS!!!!!! Damn. Aside from the nominal bearing forces, the conveyer produces no force to prevent forward motion.

 

Meanwhile, Rob is disappointed this discussion isn't taking place on aviatorchat.com.

 

Art, I have pointed out your flaws in thinking time and time again.

 

Tell me something, all of you who think that the plane will take off. If this were the case, wouldn't we spin up fighter jet wheels with pulley and dyno mechanisms, instead of using catapults to provide linear acceleration? We could speed the planes up in place, and off they would go!

 

The original question is a conundrum. And you cannot create it experimentally. Just like you can't have one plane in two cities at the same time. We've also been through the water example, doesn't work, lots of drag. (besides, ski planes sink).

Remember Art, this is a Newtonian physics problem. The bearing friction, rolling resistance of the tires, etc. are NOT part of the basic question and DO NOT need to be considered with regard to this question. Just like the basic question of which falls faster, a pound of lead or a pound of feathers, does not need to consider wind resistance with regard to the basic question.
The wind resistance is not to be cosidered in Physics 101.

In Physics 101, when giving BASIC examples of transfer of energy by describing motions of colliding pool balls, you do NOT need to consider the heat of compression when the pool balls strike each other, etc.

Read Shiggins and my reinterpretation of the basic question to one that does not create a conundrum and you will see that the question can be answered without considering friction, bearing heat, massive tire rotational acceleration etc.

Very simply: Wheel rotational speed, and even wheel rotational direction have nothing to do with the planes ability to accelerate and takeoff.

 

This is what your mental block is. The belt is not "stopping" the motion. It is simply opposing it equally. Net RESULT is that there is zero forward motion.

 

No. The conveyer doesn't make the airplane take off any faster, nor does it make it take off from a standstill. It just makes the wheels spin faster than they would under a normal take off. The plane still requires forward motion on the conveyer, and it is entirely possible to achieve it.

 

The belt, in your scenario, would be preventing the airplane from moving forward. It would cause it to have 0 groundspeed. It would stop forward motion. You have yet, in all your posts, to provide the means with which the conveyer- wheel system can oppose the thrust of the engine. It can't!

 

Art, I agree with you. But a consequence of the initial constraint in the problem is that it isn't possible! I realized this 30+ pages ago and it's not worth 15 pages of discussion, trust me.

 

Yes you could do that, it just isn't very practicle.
The short answer as to why it isn't practicle is that a spinning set of plane wheels, even if they are spinning 200 mph, don't store a lot of kinetic energy relative to the mass of the plane.

 

Mr. Payne and Shiggins are now on the board of directors of the
"The Original Question is a Conundrum Society"