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#617475 - 30/12/06 12:20 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Anonymous
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Originally posted by BlueSky:
See, this is what I'm saying. Your argument rides on a tailwind of fixed velocity. In the scenario, the conveyor moves faster and faster as engine thrust is increased, so the speed relative to the surrounding air remains zero. Here's the thing, though. The tailwind does not take the place of the conveyor. It merely serves to illustrate that the wheels can meet double the friction (just like the conveyor provides) and still take off. If the tailwind were ever-increasing to match the groundspeed of the plane, then of course the plane would not fly.
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#617476 - 30/12/06 12:21 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 12/09/00
Posts: 8375
Loc: the hue of dungeons and the sc...
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Originally posted by TJ:
AAARGGG!
The belt only moves if the plane moves....
Speed, or Movement, means relative to the world...not the belt.
My GPS will say I'm going 0 mph if I am on a tread mill that is turning at 4 mph.
If my tread mill MATCHES MY SPEED, it would be turning at ZERO MPH. You're changing the scenario. If your moving at 4mph relative to the conveyor, the conveyor thinks you are moving 4mph, regardless of what your GPS says. Therefore, the conveyor will move at -4mph. If there is someone controlling the conveyor and they are watching a pedometer you are wearing - you are going 4mph to them. So the conveyor stays at -4mph. If they are WATCHING you - they will stop the conveyor (since by observation, you aren't moving relative to them). But then you will suddenly thrust forward - and they will see they were mistaken on your speed. Basically - the question is worded poorly. It doesn't say what the speeds are relative to.
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist
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#617477 - 30/12/06 12:21 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 17/08/00
Posts: 2286
Loc: Georgia
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Originally posted by XPLORx4: Originally posted by BlueSky:
[b]The force of gravity must be overcome to move an object, whether it's up, down, forward, back, or sideways. Are you serious? What the hell do you think keeps you from moving heavy objects, regardless of the direction? It's their WEIGHT which is a measure of GRAVITY.
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#617478 - 30/12/06 12:22 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Anonymous
Unregistered
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Back to that image of the smoke trails around the wings Moby..... Showing the Airflow in a Wind Tunnel. A technique often used in wind tunnels is to introduce smoke in front of the airfoil that is being tested. The smoke comes from regularly-spaced point sources, and the wind flow in the tunnel spreads it out into parallel lines, called streamlines. The streamlines make it possible to visualize the airflow over the airfoil. When the lines continue smoothly over and past the airflow, they show that the flow remains laminar, and that the airfoil is creating very little drag. When the streamlines show more chaotic, turbulent flow, they indicate that the airfoil is creating more drag. You can do something similar with a wind tunnel by stretching thin strings across the flow path, above and below your airfoil test zone. Clip them in place so you can move them up and down to fit different airfoil shapes. Attach a ribbon (about 25 cm long) to each string. Use a stick attached to your airfoil to hold it while you place it in the flow path, between the ribbons. The ribbons will act like the smoke streamlines, so that you can visualize whether the flow over your airfoil is turbulent or laminar. Try different airfoil shapes and measure which have the most laminar and the most turbulent flow. (Parker, 2005, 18–19) Taken from HERE The smoke is released from a point on the wall, much in the same way that a rope is attached to a point on the wall  Think of the rope as a representation of a streamline...
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#617479 - 30/12/06 12:22 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 08/03/01
Posts: 7756
Loc: Lawrenceville, NJ, USA
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Point to consider: (Forget the belt thing for a minute) Ordinary plane taking off from an ordinary run way... The tires are turning at the plane's speed as it lifts off... ...the instant that the plane's tires are no longer ON the runway, they start slowing...is the plane slowing?  What if I placed some rollers on the runway EXACTLY at the POINT of lift off for the TIRES? The plane is hurtling down the runway, its tires rotating at the plane's speed.... It hits the rollers EXACTLY AT THE POINT IT WOULD LIFT OFF... The tires HAVE NO TRACTION on the rollers... They JUST SPIN UNDER THE TIRES>>>>Can the plane take off?
_________________________
- 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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#617481 - 30/12/06 12:23 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Anonymous
Unregistered
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Now I know you two are just trolling us. Ha ha, I fell for it. C'mon, quit kidding around here.
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#617482 - 30/12/06 12:23 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 12/09/00
Posts: 8375
Loc: the hue of dungeons and the sc...
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Originally posted by Hawk: Back to that image of the smoke trails around the wings Moby.....
Showing the Airflow in a Wind Tunnel. A technique often used in wind tunnels is to introduce smoke in front of the airfoil that is being tested. The smoke comes from regularly-spaced point sources, and the wind flow in the tunnel spreads it out into parallel lines, called streamlines. The streamlines make it possible to visualize the airflow over the airfoil. When the lines continue smoothly over and past the airflow, they show that the flow remains laminar, and that the airfoil is creating very little drag. When the streamlines show more chaotic, turbulent flow, they indicate that the airfoil is creating more drag. You can do something similar with a wind tunnel by stretching thin strings across the flow path, above and below your airfoil test zone. Clip them in place so you can move them up and down to fit different airfoil shapes. Attach a ribbon (about 25 cm long) to each string. Use a stick attached to your airfoil to hold it while you place it in the flow path, between the ribbons. The ribbons will act like the smoke streamlines, so that you can visualize whether the flow over your airfoil is turbulent or laminar. Try different airfoil shapes and measure which have the most laminar and the most turbulent flow. (Parker, 2005, 18–19)
The smoke is released from a point on the wall, much in the same way that a rope is attached to a point on the wall That smoke is not attached, though.
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist
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#617483 - 30/12/06 12:25 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 12/09/00
Posts: 8375
Loc: the hue of dungeons and the sc...
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Originally posted by MattyX:
Now I know you two are just trolling us. Ha ha, I fell for it. C'mon, quit kidding around here. No. I am convinced without a shadow of a doubt - if the conveyor matches the plane's speed, it will not budge. You guys go ahead and make a conveyor that can do it and go try and ride the plane. I'll stay on the ground, thank you.
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist
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#617484 - 30/12/06 12:25 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Anonymous
Unregistered
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The rope is a representation of the smoke streamlines....You need to open your mind. It's not that difficult to understand
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#617485 - 30/12/06 12:25 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
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Originally posted by Mobycat:
So someone answer this ignored comment:
If the engines are off, and if there was NO friction, and that conveyor belt moved, the plane shouldn't budge - it will just have rolling wheels. That's a correct statement if you mean there's no friction in the wheel bearings. (You need friction between the tires and conveyor, otherwise the tires wouldn't start rolling).
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#617486 - 30/12/06 12:26 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
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Originally posted by BlueSky:
What the hell do you think keeps you from moving heavy objects, regardless of the direction? It's their WEIGHT which is a measure of GRAVITY. Uh, no. That's called MASS, not WEIGHT.
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#617487 - 30/12/06 12:27 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 17/08/00
Posts: 2286
Loc: Georgia
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Finally we agree. Those clowns on the other side of the argument will NEVER understand! I'm done with this thread for now and will think on it some more, and if my opinion changes, I'm man enough to post it here and will. For now this is just spitting in the wind.
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#617488 - 30/12/06 12:27 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Anonymous
Unregistered
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Actually, you need a forward force to overcome the downward force of gravity. Once that initial downward force is overcome, yes, the plane will theoretically role freely - barring friction of course.
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#617489 - 30/12/06 12:27 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 12/09/00
Posts: 8375
Loc: the hue of dungeons and the sc...
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Originally posted by XPLORx4: Originally posted by Mobycat:
[b]So someone answer this ignored comment:
If the engines are off, and if there was NO friction, and that conveyor belt moved, the plane shouldn't budge - it will just have rolling wheels. Yes, in the wheel bearings. So, if there is friction, the plane will roll backwards? Can the plane match the force with its engines? What if it can't do anything *beyond* matching it?
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist
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#617490 - 30/12/06 12:27 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
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OK, so here's what Moby's argument boils down to (if I understand it correctly):
The plane can't take off because the rolling resistance of the tires on the conveyor and the friction of the wheel bearings resists the plane's movement through the air enough to prevent it from achieving enough airspeed to take off.
Essentially, the wheel bearings and tires are acting like big parachutes behind the plane.
The plane may actually move down the runway (it would have to have some kind of forward motion because otherwise the conveyor would also stop moving) but it'll just reach the end of the runway before getting airborne.
So, the issue essentially is that we'd have to know the design limitations of the tires and wheel bearings in order to know their maximum safe RPM before self-destructing.
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#617491 - 30/12/06 12:29 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Anonymous
Unregistered
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At this rate, this thread will take over the top spot for "Thread with the most pages". ![[LOL]](graemlins/lol.gif) Move over Phat Chicks!! The plane is taking off!!!
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#617492 - 30/12/06 12:30 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
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Originally posted by Mobycat:
So, if there is friction, the plane will roll backwards?
Can the plane match the force with its engines?
What if it can't do anything *beyond* matching it? If there's friction in the wheel bearings, then yes, the plane will roll backwards. Can the plane match the force with its engines!? I should hope so! Otherwise it needs bigger engines!
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#617494 - 30/12/06 12:32 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 12/09/00
Posts: 8375
Loc: the hue of dungeons and the sc...
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Originally posted by XPLORx4: Originally posted by Mobycat:
[b]So, if there is friction, the plane will roll backwards?
Can the plane match the force with its engines?
What if it can't do anything *beyond* matching it?
Can the plane match the force with its engines!? I should hope so! Otherwise it needs bigger engines![/b]And the last question? What's your answer?
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist
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#617495 - 30/12/06 12:33 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
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#617496 - 30/12/06 12:33 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 08/03/01
Posts: 7756
Loc: Lawrenceville, NJ, USA
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Originally posted by Mobycat: Originally posted by TJ:
[b]AAARGGG!
The belt only moves if the plane moves....
Speed, or Movement, means relative to the world...not the belt.
My GPS will say I'm going 0 mph if I am on a tread mill that is turning at 4 mph.
If my tread mill MATCHES MY SPEED, it would be turning at ZERO MPH.
If your moving at 4mph relative to the conveyor, the conveyor thinks you are moving 4mph, regardless of what your GPS says. Therefore, the conveyor will move at -4mph.
If there is someone controlling the conveyor and they are watching a pedometer you are wearing - you are going 4mph to them. So the conveyor stays at -4mph.
If they are WATCHING you - they will stop the conveyor (since by observation, you aren't moving relative to them). But then you will suddenly thrust forward - and they will see they were mistaken on your speed.
Basically - the question is worded poorly. It doesn't say what the speeds are relative to.[/b]um, relative to the planet...like what speed means. Although...this DOES clarify WHY so many of you CAN't figure this out. Speed is a universal term...but, the wrong answer people are confusing Speedometer speed with REAL speed. Speed is how quickly you cover a distance, say in miles per hour. If I am going 4 mph, I will be able to cover 4 miles in one hour. My speed on a tread mill is zero, no mater how fast the TREAD MILL IS GOING. (Assuming I don't have a heart attack, etc...) My pedometer/speedometer might SAY 4 mph...but it would be tricked into it... The speed you READ while ON a tread mill is your EQUIVALENT speed, IF IT were NOT a tread mill. Maybe that's the bone of contention...what speed means in THIS scenario? If we agree what speed means..for THIS problem...this will all fall into place?
_________________________
- 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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#617497 - 30/12/06 12:35 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
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Originally posted by Mobycat:
What if it can't do anything *beyond* matching it? Then, again, the plane needs bigger engines.
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#617498 - 30/12/06 12:35 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 09/05/02
Posts: 5232
Loc: Florida
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I have noticed that this entire discussion keeps moving in circles. ![[Freak]](graemlins/freak.gif) Please.... everyone get away from the tires...gravity...ropes...wind tunnels...pushing Xterras uphill, etc., etc. These things are confusing some and taking the discussion in directions it doesn't need to go. Originally posted by TJ:
I noticed alot of people thinking the plane would appear stationary, if the conveyor went at the plane's speed towards it.
I noticed a lot of people thinking that somehow if the conveyor went the same speed as the plane, that the plane was NOT MOVING. That is an assumption on your part. The plane is moving. However... once the conveyor and the plane's speed are matched exactly... to an outside observer the plane would "appear" to be stationary. Remember... "appear" stationary. Are we at least on the same page regarding that fact?
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#617499 - 30/12/06 12:37 PM
Re: Know that if you do not post in this thread today the human race may cease to exist
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Member
Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
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Originally posted by NY Madman:
The plane is moving. However... once the conveyor and the plane's speed are matched exactly... to an outside observer the plane would "appear" to be stationary. Remember... "appear" stationary.
Are we at least on the same page regarding that fact? I think not. The issue is how speed is measured. Is it measured in absolute speed (i.e over the earth's surface) or in relative speed (i.e. over the conveyor belt)?
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