Riddle: Airplane on a treadmil

This is a very highly debated topic, even though scaled tests have been conducted. The popular Mythbusters show on discovery did it full scale, but some still dispute the way they did it. You can probably find thousands of forums that host this same question, and I wouldn't be surprised if it has even been posted here before. So here goes!

A large passenger jet sits on a treadmill the size of a normal runway that they would normally take off on. When the jet starts up, it climbs in speed slowly. The treadmill matches the jet's speed EXACTLY. For every mile an hour the jet climbs, the treadmill goes in REVERSE that exact amount as-well.

The grand question: Will the plane take-off?

Assume that:

The wind is at 0 MPH.
The Jet is powered by turbines.

QUOTE (Rheticus @ Sep 10 2008, 10:03 AM)

Now let's move to a plane. I think we can all agree there is friction in the wheels. Everyone has said "negligable" well, in this case, any non-0 value is not negligable. So, we will say the treadmill speeds up to match the wheels speed in a near-instantaneos fashion. Let's start at time 0.

[etc...]

This is where friction comes in. Eventually, the friction (which is dependend on the wheel speed) will equal the maxiumum output of the plane. This will cause the wheels to act as a sort of anchor to the ground. Think of what would happen if you replaced the wheels with iron anchors. The plane would not move (but a lot of force would be on the connectors). Yes, it's counter intuitive, but that's what would happen.

--sigh--

This is for those of you who believe it is a realistic possibility to keep an aircraft, operating its engines at full throttle, motionless by way of wheel friction.

Let's take a typical aircraft engine: the PW 4000 series. These have a maximum thrust of at least 50,000 lb (up to 100,000 lb for some variants). This is one of the types of engine currently used on the Boeing 747-400. It has four of them. Since they will normally be taking off at full throttle, is reasonable to assume that they are, at the very least, producing some 200,000 lbs of thrust. Yes, that's right, I said two-hundred-thousand pounds of thrust, and likely more. For those of you who live in the metric world, that's roughly 1 MN. That's right: one mega-Newton. Which is a very large force. If you don't believe me, ask 500 sumo-wrestlers to sit on you.

Wheel friction, on the other hand, is a very small force. This is frequently demonstrated in land vehicles by astute passengers who notice that you can coast a really long way with the transmission in neutral. Aircraft are no different. If they were were, they would not need to install them with wheel-brakes and reverse thrust buckets to prevent them from crashing at the end of the runway after landing. Typical values of rolling friction coefficient for properly inflated rubber tires on concrete are as much as 0.01. The maximum takeoff weight of a 747-400 is about 800,000 lbs, so the rolling friction is probably less than 8,000 lbs, or 20 sumo-wrestlers. "At most 20" is a significantly smaller number than "at least 500". If you don't believe me, ask 480 mathematicians.

Finally, we have bearing friction. Under normal circumstances, bearing friction is negligible compared to other sources of loss. This is demonstrated by children around the world who like to spin the front tire of their bicycles and observe how long, with good bearings, it keeps going. A bearing loss, at its rated speed I estimate to be of the order of 5% of rolling friction (or 1 sumo wrestler). "At most 21" is still significantly smaller than "at least 500." Now, if I remember correctly, bearing friction increases approximately with the square of speed. So, in order for bearing friction to account for our remaining 480 sumo-wrestlers, the treadmill would have to be zipping along at 4,000 kts -- slightly more than 20 times the takeoff speed of the aircraft, and roughly 7 times the speed of sound at sea level and 68F.

Now, I'm no expert on such things, but I suspect that if you tried to roll a 747 along a treadmill at 4,000 kts, you might run into some kind of tire, or possibly bearing, problem. But yes, theoretically, if you had bearings made of magic fairy dust, tires stretched from Superman's scrotum, and a freaking huge hamster operating a hypersonic treadmill, you could keep a 747, with all engines at full power, completely motionless.

To conclude:
* in the universe in which we, and all other beings, live, the airplane takes off and soars through the sky;
* in Candy-coated Sugar bon-bon La-La land, where acid-flashbacks come alive, it is possible that the airplane is unable to take off.

The Notion of Family

I thought this was an interesting observation.

From Women's Voices, Feminist Visions, by Susan M. Shaw and Janet Lee, page 376, paragraph two:

"The notion of family - with all its connotations of love, security, connectedness, and nurturing - is a prime target for nostalgia in the twenty-first century. As economic forces have transformed the ways that families function, we yearn for a return to the traditional family, with its unconditional love and acceptance, to escape from the complexities and harsh realities of society..."

Take from it what you can, and what you will.

Bidwell, out.

An Interesting Forum Conversation about Disorders

Cule: I'm a midget. Not a joke.

Hostile: You expect us to believe that? It's a bit of a tall order.

Jackie: I think you're a little... short... on your smart remarks there, Hostile.

Left Foot: Don't get so high and mighty.

Hostile: Honestly, I was hoping you'd... rise above this kind of behaviour, Jackie.

Jackie: Don't think you're better because of small talk.

What's the point in trying to achieve the impossible?

Hmm. An interesting question, that.

I heard this question earlier today, from a friend.

So, the question is: Why should one try to accomplish a task, if it is impossible? In other words, why even try? I felt rather hurt that this person would say such a thing that sounds so defeatist.

Why should we try anyway? I'll tell you why: because if we don't, we are only defeating ourselves, one bad deed at a time. When we admit defeat even before the battle has begun, there's no more purpose. One pessimistic defeat entails yet another, and another, until one gives up all hope. And at that point, we break.

How many breaches in history have their been proving logic incorrect about accomplishing something that was initially thought impossible?

The world was proven not to be flat. That Portuguese explorer Magellan was the first to accomplish circumnavigation – a previously thought impossible feat.

Geocentrism was disproved when opposed to heliocentrism. As we all know, the sun IS the center of our solar system.

The undividable, Greek-named word “atom” IS actually divisible. We discovered that, though the atom was thought “indivisible”, subatomic particles were discovered easily enough.

All living organisms were defined as living components that contained DNA, RNA, or both. It's impossible to be an organism and not have DNA - at least, that was the definition of it several decades ago. But what have we found? The impossible - several viruses have been found that contain no nucleic acids, and are instead quite good at taking in DNA from the environment. It's living... and yet, has no DNA or RNA. Impossible? Hey, we're proved wrong again!

I thought it was impossible for me to find peace in my mind, one year ago. Yet here I am, straight as an arrow, thinking positive thoughts about how life can turn around in a heartbeat, whether it is or is not in your favor.

There are many examples of what I thought was impossible to achieve in my life, but the very fact that I’m still in good hands and that I have the chance to thank those who helped just proves to me, all over again, that the ‘impossible’ is no longer a feasible, or appropriate, term. I learned that the ‘impossible’ is relative. ‘Impossible’ is an illusion. ‘Impossible’ merely gives us the chance to overcome it, because ‘impossible’ means nothing.

Why won’t I try to achieve the impossible? Why not? Because it’s our inherent responsibility to do so. We are all given the chance to recover and rebuild. If we don’t take that blessing in hand and thank it, we only curse ourselves.

Don’t wait for something to happen. Humpty Dumpty is only a story.

I hope this has all been very well and inspirational to the readers. I'll be in my office; Mondays through Thursdays from 8AM - 5PM. Make an appointment.

Hey, we got a good track record going here...

Enter, Mr. Cheery Disposition.
"Hi, everyone!" says Mr. Cheery Disposition. Wave hand enthusiastically.

Doc said that if I think optimistically, it'll make me less stressed. He was also the one that said if I don't think about monsters under the bed, they won't be there. But we all see how well that turned out:


We will all learn a thing or two about Calvin and Hobbes. :) Now, onto what I was supposed to get onto a few moments ago. Actually, I was hoping to build up to it, in some kind of eerie suspense that ought to get your skin crawling around like larvae that has been dug up from a... but I digress.

The Construct forum (http://lorie.forumco.com/default.asp) has been getting an unusual amount of traffic in the past week. Insofar as I mean "unusual," I actually mean a lot. And by "a lot," I mean, 8 or 9 people at once. Hey, that's a lot!

What's the curious increase in visitors? Well, thanks to some handy advertising in the right places, it seems some people are coming to know the forum (finally). But what is discouraging is the amount of people that actually join - zero.

I usually just laugh it off, but this is seriously getting to me. You have at least 8 or 9 visitors (unique visitors!) per day, but none of them join? I did happen to block access to 2/3's of the forum if you're not a registered member (guests can only read and reply to the news section), so there's really nothing to look at, if you're not registered. There IS, however, four very tasty and short threads you can look at in the aforementioned News Section of the forum if you're NOT a member, but really, how many people do you need to stare at these before they leave? Is it the same 8 or 9 people? How long can 4 short threads entertain you? Aren't you in the least bit curious about the unkown? Don't you want to know what else is there for you to find out? Are intellects an endangered species? Do these people have some sort of aphasia?

Sorry. Had to vent. My mistake. Here, this ought to make you happy:


I know that made me happy. The question is now, will you let it make you happy as well?

That's our philosophical question for today. Take from it what you can, and what you will.

"Good day, Bidwell." Bow out.
Curtains.

Happy Birthday, my love! :D

Today, the 26th of March, 2007, is the first birthday that my girlfriend will be experiencing with myself. :) It's history in the making, baby!

I want to wish you, my love, a very happy and joyful birthday, because I'll be here to make it fun and I'll still be here to take care of all those other years.

Because I'm a kitty cat. Meow meow. :)

I love you, Lorie! You're moving on to your Golden Years. And I'm very glad to experience it with you.

Did you get my presents yet? Hahahah. :P

i have the key to the city!

of the limiting reactant, that is. hi im lorie, friend-girl of josh. i'm not much of a blogger, although i'll try to post whenever inspiration tickles a lobe or two. i AM however, a forumite. please come and visit The Construct. its a forum you'll be able to access by clicking one of the threads above. hope to converse with you soon! :) meow mix!

Meow Mix!

Hello, thar!

I wish I could create time, but unfortunately (or fortunately, depending how you view it), I cannot.

If I could create time, I would most definitely use it to visit my better half (who lives in a different time zone), and spend about a year catching up. We'd hug, kiss, cuddle, walk through parks and watch the sun and stars when they show themselves in the sky. Then, together, we'd probably study for our classes for another couple months or so until we're both caught up until we're two years ahead of the class of '09 :P

Well, that's enough for me and wishing. It's time to acknowledge all the blessings I've had the luxury to have - and the firstmost blessing that I would like to mention is my significant other, Ma Lorie Ann. What did I do to come into a relationship with this angel? I certainly have no idea, and the moments that I think I do I remain humble anyway... so let's leave this one, as deserving, to God. Thank you God, for your kindness among us.

To love is to feel something you've never really knew you haven't experienced until you experience it for the first time. I'm not sure if the previous sentence made sense or not, or if it was just a "no-duh" kind of thing, but I'm sure the reader understands what I'm trying to say.

One should always love unconditionally. Conditional love is not something that anyone deserves. Everyone deserves love, no matter what happens in life. Nothing less is sufficient.

You, Ma Lorie Ann, give me that unconditional love. This love, which is so different and much more amazing than any other feeling that I have ever felt before, is the best kind of love - the love that will remain in my heart, in my mind and in my soul, until we return to dust. The kind of love that assures you in your insecure moments at night, and also the one that will watch over your relationship through all the bad and the good.

That's what love is. That's what I have now. Thank God, and thank you Ma Lorie Ann.

Knocking on your Door! :]

La's boyfriend reporting. :P Sorry to completely deceive you! I have an important message for all of you.

I'll be seeing La again, very soon, for the third time after the end of this semester. I very much hope (depending on my parent's ultimate decision [yes, I'm still not yet a man of my own destiny yet :P]).

Looking for special things inside of me.

Oh, dear me, I think heart pressure increased by a factor of two and a half. So is this what it's like to be madly in love? Is this what I've been waiting for the majority of my life that I've felt lack?

Love is such a strange, interesting, undefinable and amazing feeling. Don't you all agree? It cannot be grasped easily, like a bar of soap that has been used one too many times. It cannot be quantified, as some people try to do, in numbers, equations or online websites. You cannot give an objective definition of it without using a subjective term or word. And love is one of the most amazing things that you can experience. I'm not saying this as a wide-eyed teenager madly in love (with all the hormones and such), but this is a long-distance relationship.

I'm saying this as a wide-eyed five-year-old boy, who is lost in his elementary school, desperately looking for someone to cry on. Looking for someone's skirt or pant leg to hold on to as I walk down the hall. I'm looking for someone that would hold me when I stumble, from fear, weakness or fatigue, or the unknown.

They say in the darkest night, there's a light beyond.

I try to turn a blind eye to those people who treat me as a person that couldn't take care of himself without everybody helping him, especially in my intimate relationship with La. I'm not a naive person when it comes to relationships, especially on how much (everything!) I give myself to La. It is exilharating, and where it was once terrifying, a sense of security lays itself down on my lap, like a reassuring warmth from a small cat that wants attention.

Who can ignore a cute kitty?

I'd wait and wait and wait yet some more for you, La. I'd go anywhere and do anything you'd ask... no matter how ridiculous sounding or ludicrous - and I'd do it with a full and sincere heart, out of love. Again, what is love?

I can't put it in words (and I think the word itself in English doesn't pay it nearly enough justice), so I'll attempt to describe it. Love, in my opinion, is when you have a very, very, very deep and intimate relationship with someone that you'd want to spend your life with. This person knows all about you, thinks like you, loves like you, and aspires like you, and with you, throughout your life, and proves it to not only you but others as well (time and again!) that he or she is completely for you and no one else. You reserve nothing of your persona, as you trust them completely with everything that you are and everything you have.

Is that it?

I love you, La. More than anything.

I'm alive... the defibber is on standby.

Hey everyone! I'm sorry about the complete and pitiful lack of posts.

If you'd like to find the whole story (which I do not have time to duplicate on this site), please visit the forums at this link in the announcements section:

http://lorie.forumco.com/forum~FORUM_ID~6.asp

I hope to get back to you all soon! Don't worry, I didn't forget anybody. :]