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#617650 - 31/12/06 12:27 PM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
You guys are smoking something. If the wheels don't move, and they're attached to the plane, I have news for you. The plane isn't moving either. As thrust is applied, the wheels will just rotate faster because the belt accelerates to keep up.

At least that's the way it works in my world. If it's different in yours, so be it. cool

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#617651 - 31/12/06 12:28 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


lol, 39 pages

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#617652 - 31/12/06 12:32 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by BlueSky:
You guys are smoking something. If the wheels don't move, and they're attached to the plane, I have news for you. The plane isn't moving either. As thrust is applied, the wheels will just rotate faster because the belt accelerates to keep up.

At least that's the way it works in my world. If it's different in yours, so be it. cool
Hell, man, the original problem statement didn't even say the plane HAS wheels... It could be sitting on skids or floats... So then what happens? The plane still takes off... There's just more friction between the plane & the conveyor belt.

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#617653 - 31/12/06 12:35 PM Re: Know that if you do not post in this thread today the human race may cease to exist
slomatt Offline
Member

Registered: 10/04/02
Posts: 165
Loc: Bay Area, CA
Quote:
Originally posted by BlueSky:
You guys are smoking something. If the wheels don't move, and they're attached to the plane, I have news for you. The plane isn't moving either. As thrust is applied, the wheels will just rotate faster because the belt accelerates to keep up.

At least that's the way it works in my world. If it's different in yours, so be it. cool
Except that this isn't a difference of opinion, people have posted proof that the plane will take off using valid physics.

Perhaps the only way to prove this to everybody is to call up the Myth Busters? smile

- Matt

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#617654 - 31/12/06 12:46 PM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Quote:
Originally posted by slomatt:
Quote:
Originally posted by BlueSky:
[b]You guys are smoking something. If the wheels don't move, and they're attached to the plane, I have news for you. The plane isn't moving either. As thrust is applied, the wheels will just rotate faster because the belt accelerates to keep up.

At least that's the way it works in my world. If it's different in yours, so be it. cool
Except that this isn't a difference of opinion, people have posted proof that the plane will take off using valid physics.

Perhaps the only way to prove this to everybody is to call up the Myth Busters? smile

- Matt[/b]
They SAY it's valid physics and post an impressive looking formula. Well, I'll be the first to admit that I personally can't refute it because I don't have the knowledge of physics or mathematics. But that doesn't make it right.

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#617655 - 31/12/06 12:48 PM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Quote:
Originally posted by porsche996:
Quote:
Originally posted by BlueSky:
[b]You guys are smoking something. If the wheels don't move, and they're attached to the plane, I have news for you. The plane isn't moving either. As thrust is applied, the wheels will just rotate faster because the belt accelerates to keep up.

At least that's the way it works in my world. If it's different in yours, so be it. cool
Hell, man, the original problem statement didn't even say the plane HAS wheels... It could be sitting on skids or floats... So then what happens? The plane still takes off... There's just more friction between the plane & the conveyor belt.[/b]
You're most amusing. If you applied thrust with the plane on skids or floats, the plane would nose over just like somebody going downhill on a bike who locks up the front brakes. That pesky friction again.

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#617656 - 31/12/06 01:16 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
Quote:
Originally posted by BlueSky:
Quote:
Originally posted by XPLORx4:
[b]Great. On a windless day, if the engines are off the aircraft has neither airspeed nor groundspeed.

OK, now, let's place a conveyor belt under the aircraft's wheels, and bolt the plane to the ground by its nose, tail,and wingtips. Now, let's fire up the conveyor belt to 100mph.

It's still a windless day.
Answer these questions:
1) What's the aircraft airspeed?
2) What's the aircraft groundspeed?
3) What's the aircraft's wheelspeed on the conveyor?
1) Zero
2) Zero
3) I'm not sure what you mean. All over this thread, people have said "the wheels are turning at X MPH." But speed is a measure of movement, and the wheels aren't moving (except for rotation), so it should really be measured in RPM, right? Can you clarify please?[/b]
The conveyor belt has a surface speed of 100mph, right? The RPM of the tires over the conveyor belt is determined by the size of the tire, but we don't care about the tire RPM, we care about the speed at which the tread of the tire is moving, which is... 100mph! Right?
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617657 - 31/12/06 01:21 PM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Quote:
Originally posted by XPLORx4:
Quote:
Originally posted by BlueSky:
[b]
Quote:
Originally posted by XPLORx4:
[b]Great. On a windless day, if the engines are off the aircraft has neither airspeed nor groundspeed.

OK, now, let's place a conveyor belt under the aircraft's wheels, and bolt the plane to the ground by its nose, tail,and wingtips. Now, let's fire up the conveyor belt to 100mph.

It's still a windless day.
Answer these questions:
1) What's the aircraft airspeed?
2) What's the aircraft groundspeed?
3) What's the aircraft's wheelspeed on the conveyor?
1) Zero
2) Zero
3) I'm not sure what you mean. All over this thread, people have said "the wheels are turning at X MPH." But speed is a measure of movement, and the wheels aren't moving (except for rotation), so it should really be measured in RPM, right? Can you clarify please?[/b]
The conveyor belt has a surface speed of 100mph, right? The RPM of the tires over the conveyor belt is determined by the size of the tire, but we don't care about the tire RPM, we care about the speed at which the tread of the tire is moving, which is... 100mph! Right?[/b]
How are you calculating that?

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#617658 - 31/12/06 01:28 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
Quote:
Originally posted by BlueSky:
How are you calculating that?
Look, you should know that tire size and forward speed are irrelevant to each other. An Xterra with 35" tires and an Xterra with 31" tires can both keep up with each other, right? They both can use GPS to travel at 60mph, right? But their speedometers are different because their tires are rotating at different RPM. Cars use rotational sensors, multiplied by the differential gear ratios, multiplied by the stock OEM tire diameter to provide accurate speed.

So, in our plane's tires, if the tires are really big or really small, their tread is still moving at the surface speed of the conveyor belt, right? So, if the conveyor belt is going 100mph, and the plane is bolted to the ground on a windless day:

1) What's the airspeed? 0 mph
2) What's the groundspeed? 0 mph
3) What's the tire tread speed? 100 mph

Do you agree?
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617659 - 31/12/06 01:32 PM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Quote:
Originally posted by XPLORx4:
Quote:
Originally posted by BlueSky:
[b]How are you calculating that?
Look, you should know that tire size and forward speed are irrelevant to each other. An Xterra with 35" tires and an Xterra with 31" tires can both keep up with each other, right? They both can use GPS to travel at 60mph, right? But their speedometers are different because their tires are rotating at different RPM. Cars use rotational sensors, multiplied by the differential gear ratios, multiplied by the stock OEM tire diameter to provide accurate speed.

So, in our plane's tires, if the tires are really big or really small, their tread is still moving at the surface speed of the conveyor belt, right? So, if the conveyor belt is going 100mph, and the plane is bolted to the ground on a windless day:

1) What's the airspeed? 0 mph
2) What's the groundspeed? 0 mph
3) What's the tire tread speed? 100 mph

Do you agree?[/b]
Yes, I know all that. So answer my question.

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#617660 - 31/12/06 01:34 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


I dunno...

Most of the people did a pretty good job explaing why exactly the plane WOULD move, and how it will be achieve. I guess it's hard for some to visualize. You're still imagining a scenario when the wheels would be delivering power to ground but they are not.

I like the "plane on ice" analogy. On perfect ice, the plane wheels would not spin, but simply slide along the ice with the plane moving forward once the engines are fired, resulting in the plane taking off.

In this scenario, ice is what eliminated the friction and allowed the place to move and take off.

With out original given scenario, it's the tires that are eliminating friction (perfect world with no rolling resistance, for the same of my point). Since there's no friction, it doesn't matter how fast the conveyor belt moves. It can move at 200 mph, BUT THE PLANE WOULD BE STILL WITH ENGINES OFF. I hope you're with me.

Now add the thrust of the engine. Bam! The plane takes off because the engine THRUST offsets the equilibrium of forces (again, keep in mind, we are not taking into consideration the rolling resistnace of tires and bearings).

If after 39 pages it's still not clear, I give up. [Laughing]

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#617661 - 31/12/06 01:38 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
Quote:
Originally posted by BlueSky:
Yes, I know all that. So answer my question.
So what's your question? How I'm calculating the speed of the tire tread?

The speed of the tire tread that's in contact with the conveyor belt, relative to the plane that's bolted to the ground is equal to the speed of the conveyor belt, assuming that the tire isn't skidding.

The speed of the tire tread that's on the TOP of the tire is traveling at the negative speed of the conveyor belt.

So, if the conveyor is going 100mph towards the rear, the bottom of the tire tread is also going 100mph towards the rear, but the top of the tire tread is going 100mph towards the front.

But none of this matters anyway, because the wheel axle isn't moving. It's still bolted to the aircraft, which is bolted to the ground.
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617662 - 31/12/06 01:44 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Rockaholic Offline
Member

Registered: 18/02/02
Posts: 1632
Loc: Reading, MA
Quote:
Originally posted by BlueSky:
[QUOTE]Originally posted by XPLORx4:
[qb] Yes, I know all that. So answer my
question.
You stil haven't answered mine, so why should he answer yours?
_________________________
Jeffrey
I'm just trying to put my tires on the rocks of life.

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#617663 - 31/12/06 01:45 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
I'm trying to establish that the "tire tread" speed has no relevance to the plane's groundspeed or airspeed. You already accepted that the airspeed and groundspeed are both ZERO, in spite of the fact that the tires are turning beneath the plane.
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617664 - 31/12/06 02:12 PM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Quote:
Originally posted by Rockaholic:
Quote:
Originally posted by BlueSky:
[b][QUOTE]Originally posted by XPLORx4:
[qb] Yes, I know all that. So answer my
question.
You stil haven't answered mine, so why should he answer yours?[/b]
Go back in your corner. He can handle his own conversation.

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#617665 - 31/12/06 02:15 PM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Quote:
Originally posted by XPLORx4:
I'm trying to establish that the "tire tread" speed has no relevance to the plane's groundspeed or airspeed.
If you're saying the rotation speed of the tire is irrelevant to the forward movement of the plane, I'd agree because as thrust is applied, if the plane starts to move forward the belt accelerates. The tires spin faster but the plane still doesn't move.

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#617666 - 31/12/06 02:27 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


The answer is the conveyor can never stop the plane from moving. Forward motion is provided by an external force outside the conveyors control. What does the plane care how fast the conveyor is moving? It's relative motion to a stationary object is unaffected by the conveyor.

I thought the walkway and tow rope explaination worked but some of you guys ignored it.

Take a toy car and stick it on a treadmill... Hold it in your hand and turn the treadmill on. The wheels spin matching the speed of the conveyor. Move your arm forward and backward relative to the conveyor. Does the conveyor speed affect your ability to move the car faster or slower on the conveyor?

Turn the speed up on the treadmill. Standing off to the side, can you still push the car towards the front of the conveyor? Was there enough resistance to make it impossible to move the car forward?

The wheel speed is independent of motion of the car on the treadmill because it's means of propulsion (your hand/arm) is independent of the treadmill.

Now a normal car being driven by the wheels on the same conveyor would go no where relative to objects not on the conveyor.

Man I hope this helps.

I'm starting to think you're just jerking us around to see how long we'll try to explain it before we get frustrated to the point of exhaustion.

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#617667 - 31/12/06 02:45 PM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Who knows, maybe you guys are right. I see your point about the toy car, but in that example, the treadmill's speed is constant.

In answer to your question, I'm not jerking anybody's chain. It seems to me you can use maximum thrust and if the belt speeds up also, it's not going to move.

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#617668 - 31/12/06 02:55 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Even if the treadmill speed varies, would it affect the car as long as you are providing the motion? The motion is provided by you not the treadmill.

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#617669 - 31/12/06 03:12 PM Re: Know that if you do not post in this thread today the human race may cease to exist
TJ Offline
Member
*****

Registered: 08/03/01
Posts: 7756
Loc: Lawrenceville, NJ, USA
laugh

Damn

We're still on this?

Its the speed thing...

the ONLY thing KEEPING the last to see the light is the Speed issue.

EVERYONE else knows that the speed of the plane is how fast IT IS MOVING, and

NOT

How fast its tires are SPINNING.

If you think that the SPEED of the plane is the speed of its tires' rotation (Like off a speedometer of a truck doing a burn-out)..

THEN

you come to the wrong conclusion...and think the plane is not moving.

Of course, if its not moving...there's no conveyor speed to match.

So - One camp is saying the plane sits there on a stationary/non-rotating conveyor belt.

(Because there's nothing to make the plane turn its tires, except it moving)

AND

It can't move unless the engine pushes it

AND

The engine can ONLY push the plane like the finger pushing the toy truck.

_______

In the world of the CF'r:

The finger pushes the truck...but, some how, it does not move forward.
_________________________
- TJ

2001 Xterra '03 VG33, SE 5 spd, 305/70/16's, Revolvers, UBSkidderz, Doubled AAL's, 3"SL/2"BL, winch/bumpers, skids, sliders, OBA, Snorkel, pine stripes....

Friends don't let friends drive stock.

http://www.gifsoup.com/view/501230/tj-tackling-crawlers-ridge-o.gif

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#617670 - 31/12/06 05:20 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Paul H Offline
Member

Registered: 23/08/01
Posts: 4757
Loc: Mt. Zion, IL
Quote:
Originally posted by Timmah:
Even if the treadmill speed varies, would it affect the car as long as you are providing the motion? The motion is provided by you not the treadmill.
Yes.

Same as the rope with guy on treadmill on skates. Sure you can pull yourself forward. But increase the speed of the treadmill as you do so. It will become harder to pull yourself forward. Just as with the toy car. Sure you can push it. But it will be harder as you increase the speed. Eventually the engines will reach max thrust and will go forwad no more.

I am not confused thinking the wheels deliver power.
_________________________
2001 Super Black XE R.I.P. 09/05/06
My Blog

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#617671 - 31/12/06 05:23 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Paul H Offline
Member

Registered: 23/08/01
Posts: 4757
Loc: Mt. Zion, IL
Quote:
Originally posted by JeffW:
Obviously people who have never taken a physics class find this tuff hard to grasp.

Please prove this answer wrong:
(since you claim it is incorrect)

Quote:
Originally posted by JeffW:
Relavent information:

A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?

Let's agree on what assumptions are sensible then. All of the assumptions below apply to virtually all aircraft.

Plane is powered by engines that push air (props or jets)
Plane's speed is measured by a windspeed meter as well as GPS
Plane's wheels spin freely
Wheel friction is negligible when compared to thrust
Newtonian physics apply



Coefficient of dynamic friction:

Force of friction:

F(f) = -uN

(negative because it opposes motion)

u = coefficient of static friction

N = weight of plane

Notice velocity is not included!

That means that the velocity of the conveyor belt is irrelevant for all practical purposes.

F(t) is force of thrust

a = (F(t)+F(f))/m

You won't find a scenario where |F(f)| is greater than |F(t)|. Therefore, in ALL cases the plane moves with respect to the atmosphere, thus achieving lift.

Possible scenario:

t = 0 :

Plane 0 mph
Conveyor 0 mph
Wheels 0 mph

t = 15 :

Plane 60 mph
Conveyor 60 mph
Wheels spin @ 120 mph

t = 55:

Plane 160 mph
Conveyor 160 mph
Wheels spin @ 320 mph

....

The plane takes off.

Either learn why it is correct or refute it....

..scientifically.
Guess those who took physics didn't take spelling.

And in your formula wait someone else posted that. It their formula it clearly states as long as the thrust is enough to overcome the friction then the plane takes off. I agree.

I just don't think the engines will with the counter action of the belt. Thatís me and my opinion.

Now come up with your own.
_________________________
2001 Super Black XE R.I.P. 09/05/06
My Blog

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#617672 - 31/12/06 06:20 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


yes, ever so slightly more difficult to move forward but not enough to stop you from moving the car forward.

That is friction. Other than the minute friction from the wheels rolling along it won't stop the toy car/plane from moving forward.

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#617673 - 31/12/06 06:25 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Xorand Offline
Member

Registered: 02/04/03
Posts: 2163
Loc: LA (Lower Alabama)
I've figured it out:

42
_________________________
2002 Just Blue XE 4x4

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#617674 - 31/12/06 06:28 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


[LOL] 40 pages!!! The plane is moving down the runway to take-off as the top page holder!! WOO HOO!!!

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