how the fuck do people not understand this simple concept?
when i was first asked this question my response was "duh the plane will move forward because the wheels spin freely. there might be some friction.. wheels might not be able to spin fast enough but w/e this is meant to be an idealized experiment anyways, right?"
The principals of the car will work on the moon(a moon buggy) and the airplane won't. If someone can't understand why then they will never understand the experiment or land speed vs. airspeed & lift.
Stated another way, you can answer this for yourself by asking the correct question and ignor all the things meant to confuse and distract you from this simple question: "Is there normal air flow over the wings?". Now, if you have the basic analytical ability to answer this question yourself, then Myth Busters is definitely NOT for you. Otherwise, just know that you're being ENTERTAINED - not educated. Facts and conclusions are often irrelavent. Don't be a fool. Consult credible educators.
Don't be a fool. As an airline captain with 30 yrs flying experience in all types and conditions(including catapult launches in fighters from navy carriers, I warn you, folks, beware of T.V. deceptions about conveyors, wheels, cars, all stuff that insults even average intelligence. Tests are sloppy & edited. In this case, one governing physical principle simplifies this conveyor "myth" (insult). The answer is so SIMPLE. Look up "The Bernouli Principle" and apply your God-given intelligence.
Changing the parameters of the experiment invalidated the experiment. Speed is only measurable if there is a relationship between two points. When the car's speed was measured, it was measured in relation to a point on the belt. The plane's speed was measured in relation to the air, hence the ground, since it was dead calm at the time. For validity, the plane's speed should have been measured relative to the belt, just as the car's speed was. This did not happen - experiment invalidated.
Perhaps thay should have used a glider and used the toy car to tow it to launch speed on the ground, then set the conveyor belt to that speed and put the tow car and glider on the conveyor.
That's the long way of saying Mythbusters got it wrong.
RC, you completely changed the parameters of the experiment. Of course if the source of the airplane's locomotion comes from the car towing it, there will be no takeoff. That, in fact, is what they proved. A cars locomotion is different than an airplane's.
It doesn't matter how fast the conveyor is going, an airplane will never be stationary on it. As long as the airplane is propelled forward by its prop and its wheels are free to spin, it will always accelerate forward.
@billsparky16 Real things have friction. "Free-spinning" wheels aren't totally free-spinning.
A plane with a weak enough prop would travel backwards along the treadmill. At a certain thrust level, it would be stationary with respect to the ground. At a higher thrust level, it would begin to move forward as in your simplified example.
@yushis1 The static friction is going to be out of the question as soon as the plane starts moving a tiny bit. Then you only have to worry about the dynamic friction, which has very little influence. The static friction would be the same on a conveyor belt as on the ground. Ergo, if the engine is so weak that it can't overcome the static friction on the conveyor belt, it would be so weak that it couldn't even move when standing on normal ground either.
The confusion comes from how the problem is defined. The spirit of the question is not that the plane is travelling at airspeed x and the conveyor belt is travelling at x in the opposite direction (which is Mythbusters take on the matter), it is that the belt and plane are working against each other such that the plane is stationary in relation to the ground. If the plane is stationary in relation to the ground, then no significant air movement occurs over the wing, so no lift is generated.
Of course a plane wouldn't takeoff if it's not moving, but how would you stop a plane from moving by using a conveyor belt in the first place. That just wouldn't happen in reality. The plane's wheels are free-spinning and don't affect the plane's movement, aside from the slight friction. There's no way to stop a plane from moving forward using a conveyor belt, unless you tie the plane down or hold the brakes.
Exactly! If done "correctly" then the car would not be held by treadbelt. If the treadbelt above matched the CAR'S AIRSPEED (as they do with the plane) then the car would NOT be held to 0 IAS either.
But with the car, the treadbelt is matching car's WHEELSPEED; thus car has no IAS.
IF they'd done the same with the plane (treadbelt matches wheelspeed) then the PLANE would have 0 IAS as well!
(IAS = Indicated Air Speed).
Mythbusters gave bogus example and has flawed logic.
What do you mean done "correctly"? There is no correct way to do it. It's a myth. For a car, the conveyor belt does affect it, but of course if the speeds aren't matched, it is going to travel in the direction of greater speed. If the car's speedometer reads 20 mph and the conveyor belt is traveling the opposite direction at 15 mph, then the car will go forward at 5 mph. That's because a car is propelled by its wheels pushing against the ground.
I see what you mean by done "correctly" and yes you're right. But cars have nothing to do with the myth. They just included them to show the difference in how cars and planes are propelled. The myth was that a conveyor belt could stop an airplane from taking off. And it can't. I don't know where that myth came from or how it got so big, but anyone who knows something about airplanes and physics would've known the result for sure without the Mythbusters having to do anything.
I'm glad they did the show though, because it's hard for many people to visualize or understand things like that, but they did a good job of explaining.
@johnboozer ok i'm just reading this months later...
The planes "wheel-speed" is the distance the wheel travels across a surface over time. even if that surface happens to be moving. The car can never match the wheel-speed of the plane on the belt because the wheel-speed "W" of the plane will always be equal to the planes actual groundspeed "A" plus the cars groundspeed "C" W=A+C A cannot be eliminated because its thrust comes from the propellers. And so the plane takes off.
You measure a plane's speed through the air, not over the ground. Matching the conveyor's speed means the plane's forward airspeed is equal to the conveyor's backward speed. Since the wheels do not propel the plane, the conveyor has no effect. The plane moves forwards regardless of the motion of the conveyor belt. The plane and conveyor can't work against each other since they are essentially disconnected by the wheels.
well, you've hit on the essential sticking point, and that is inturpretation of the question. Your inturpretation gives the plane airspeed by very default, so the presence of a treadbelt is moot, thereby making it a non-sencecal question.
I, on the other hand, measure the plane's speed the same as anything else (car, jogger, boat) and measure the speed of the object in relation to the surface upon which it travels (treadbelt surface).
When done this way (as the Myth Busters did with their car example) then when the plane moves forward, the treadbelt will speed up fast enough to match the plane's wheelspeed and create enough opposing force through the tires to cause the plane to have 0 airspeed.
Think about it....if the Mythbusters measured car's airspeed (like your plane interpretation) then the car would run off the end of the treadbelt!! Just think about it.
All I ask is consistency, then the results will be the same!
@jackdinn1975 The car's speed in relationship to the ground (under the treadmill) was 0. The Mythbusters did properly conduct the experiment. The airplane moved forward (relative to the Earth) at 20 mph while the conveyor belt moved backwards (relative to the Earth) at 20 mph. That's why the Mythbusters included teh cones as a point of reference. Your complaint demonstrates your own fundamental misunderstanding of the principles involved, not why they got it wrong.
But in the car's example, the belt moves 20mph in one direction...and the car goes 0mph in the other direction. Same reference, speeds were NOT matched!! Period.
Apples to Oranges my friend.
OR--"Vehicle's" speed is determined by reference to the surface upon which it is traveling. Belt = 20mph, airspeed = 0 mph, = plane does not fly.
(add as many 0's to the figures above, and the answer remains the same...NO FLY!!!!)
I understand your point with the car thing, but that does not change the fact that a conveyor belt going any speed cannot hold an airplane stationary.
@johnboozer An airplane, however, moves forward by pushing against the air. The engines are in no way connected to the wheels. The wheels are free spinning. Only wind affects an airplane's takeoff ability, not anything that has to do with the ground. Of course if the airplane's wheel speed matches the conveyor belt speed it won't move, but that would only happen if the wheel bearings were completely frictionless and the engine was off or at idle.
That's not reality. As soon as the engine is producing enough thrust, the airplane will accelerate forward, even if the conveyor belt is spinning the wheels at a million rpm.
now i get it, but my friends told me that there its a diffrent story with jet planes.
which is not as i see because same story - the engine moves the jet engine in the back of the plane and not the wheels.
The only way the plane wont move is the belt speed is so big that it melts and sticks the wheels to the runway.
TheVrdlfe 2 months ago
wow americans are dumb. here are the following ages at which other countries would fully understand this.
Japan = 5
england = 6
france = 7
lebanon = 7
italian 6
australia = 8
canada = 9
america = 48
nick081980 5 months ago
how the fuck do people not understand this simple concept?
when i was first asked this question my response was "duh the plane will move forward because the wheels spin freely. there might be some friction.. wheels might not be able to spin fast enough but w/e this is meant to be an idealized experiment anyways, right?"
sharpnova2 6 months ago
wtf i want to see the whole thing wheres the rest of it.
MegatronSmurf 8 months ago
my nephew got this first time and he's 7.
I feel sorry for my physics teacher now...
pipmdirector 1 year ago
The principals of the car will work on the moon(a moon buggy) and the airplane won't. If someone can't understand why then they will never understand the experiment or land speed vs. airspeed & lift.
vsop333 1 year ago
Stated another way, you can answer this for yourself by asking the correct question and ignor all the things meant to confuse and distract you from this simple question: "Is there normal air flow over the wings?". Now, if you have the basic analytical ability to answer this question yourself, then Myth Busters is definitely NOT for you. Otherwise, just know that you're being ENTERTAINED - not educated. Facts and conclusions are often irrelavent. Don't be a fool. Consult credible educators.
Govner2 1 year ago
Don't be a fool. As an airline captain with 30 yrs flying experience in all types and conditions(including catapult launches in fighters from navy carriers, I warn you, folks, beware of T.V. deceptions about conveyors, wheels, cars, all stuff that insults even average intelligence. Tests are sloppy & edited. In this case, one governing physical principle simplifies this conveyor "myth" (insult). The answer is so SIMPLE. Look up "The Bernouli Principle" and apply your God-given intelligence.
Govner2 1 year ago
Changing the parameters of the experiment invalidated the experiment. Speed is only measurable if there is a relationship between two points. When the car's speed was measured, it was measured in relation to a point on the belt. The plane's speed was measured in relation to the air, hence the ground, since it was dead calm at the time. For validity, the plane's speed should have been measured relative to the belt, just as the car's speed was. This did not happen - experiment invalidated.
RCbeastly 1 year ago
A car can't take off on a conveyor belt...
hobgoblinlkjfdsa 1 year ago
Good...
Dyscovery Brasil, cut this scene
VictorTheLegend 3 years ago
Perhaps thay should have used a glider and used the toy car to tow it to launch speed on the ground, then set the conveyor belt to that speed and put the tow car and glider on the conveyor.
That's the long way of saying Mythbusters got it wrong.
RCbeastly 3 years ago
RC, you completely changed the parameters of the experiment. Of course if the source of the airplane's locomotion comes from the car towing it, there will be no takeoff. That, in fact, is what they proved. A cars locomotion is different than an airplane's.
It doesn't matter how fast the conveyor is going, an airplane will never be stationary on it. As long as the airplane is propelled forward by its prop and its wheels are free to spin, it will always accelerate forward.
billsparky16 3 years ago 9
@billsparky16 Real things have friction. "Free-spinning" wheels aren't totally free-spinning.
A plane with a weak enough prop would travel backwards along the treadmill. At a certain thrust level, it would be stationary with respect to the ground. At a higher thrust level, it would begin to move forward as in your simplified example.
yushis1 10 months ago
@yushis1 The static friction is going to be out of the question as soon as the plane starts moving a tiny bit. Then you only have to worry about the dynamic friction, which has very little influence. The static friction would be the same on a conveyor belt as on the ground. Ergo, if the engine is so weak that it can't overcome the static friction on the conveyor belt, it would be so weak that it couldn't even move when standing on normal ground either.
DavidLarsenM1 2 months ago
@billsparky16 exactly.
sharpnova2 6 months ago
your an idiot, you want a non moving glider to take off!!! for cryin out loud think
bosupport 2 years ago
The confusion comes from how the problem is defined. The spirit of the question is not that the plane is travelling at airspeed x and the conveyor belt is travelling at x in the opposite direction (which is Mythbusters take on the matter), it is that the belt and plane are working against each other such that the plane is stationary in relation to the ground. If the plane is stationary in relation to the ground, then no significant air movement occurs over the wing, so no lift is generated.
jackdinn1975 4 years ago
Of course a plane wouldn't takeoff if it's not moving, but how would you stop a plane from moving by using a conveyor belt in the first place. That just wouldn't happen in reality. The plane's wheels are free-spinning and don't affect the plane's movement, aside from the slight friction. There's no way to stop a plane from moving forward using a conveyor belt, unless you tie the plane down or hold the brakes.
jetengine7 3 years ago 2
thank you
smart people do exist
thank you
bosupport 2 years ago
Exactly! If done "correctly" then the car would not be held by treadbelt. If the treadbelt above matched the CAR'S AIRSPEED (as they do with the plane) then the car would NOT be held to 0 IAS either.
But with the car, the treadbelt is matching car's WHEELSPEED; thus car has no IAS.
IF they'd done the same with the plane (treadbelt matches wheelspeed) then the PLANE would have 0 IAS as well!
(IAS = Indicated Air Speed).
Mythbusters gave bogus example and has flawed logic.
johnboozer 3 years ago
Thats what they proved, your an idiot
bosupport 2 years ago
@johnboozer
What do you mean done "correctly"? There is no correct way to do it. It's a myth. For a car, the conveyor belt does affect it, but of course if the speeds aren't matched, it is going to travel in the direction of greater speed. If the car's speedometer reads 20 mph and the conveyor belt is traveling the opposite direction at 15 mph, then the car will go forward at 5 mph. That's because a car is propelled by its wheels pushing against the ground.
jetengine7 2 years ago
Done "correctly" means "consistently" between the car and plane.
Car = The treadbelt speed was set to = car's wheelspeed
Plane = The treadbelt was set to = plane's airspeed
if the treadbelt was set to plane's wheelspeed (like the car) then yes the plane would not move 'forward' through the air, thus no flight.
johnboozer 2 years ago
I see what you mean by done "correctly" and yes you're right. But cars have nothing to do with the myth. They just included them to show the difference in how cars and planes are propelled. The myth was that a conveyor belt could stop an airplane from taking off. And it can't. I don't know where that myth came from or how it got so big, but anyone who knows something about airplanes and physics would've known the result for sure without the Mythbusters having to do anything.
jetengine7 2 years ago
I'm glad they did the show though, because it's hard for many people to visualize or understand things like that, but they did a good job of explaining.
jetengine7 2 years ago 5
@johnboozer ok i'm just reading this months later...
The planes "wheel-speed" is the distance the wheel travels across a surface over time. even if that surface happens to be moving. The car can never match the wheel-speed of the plane on the belt because the wheel-speed "W" of the plane will always be equal to the planes actual groundspeed "A" plus the cars groundspeed "C" W=A+C A cannot be eliminated because its thrust comes from the propellers. And so the plane takes off.
0Soule0 1 year ago
You measure a plane's speed through the air, not over the ground. Matching the conveyor's speed means the plane's forward airspeed is equal to the conveyor's backward speed. Since the wheels do not propel the plane, the conveyor has no effect. The plane moves forwards regardless of the motion of the conveyor belt. The plane and conveyor can't work against each other since they are essentially disconnected by the wheels.
petem1989 3 years ago 2
well, you've hit on the essential sticking point, and that is inturpretation of the question. Your inturpretation gives the plane airspeed by very default, so the presence of a treadbelt is moot, thereby making it a non-sencecal question.
I, on the other hand, measure the plane's speed the same as anything else (car, jogger, boat) and measure the speed of the object in relation to the surface upon which it travels (treadbelt surface).
johnboozer 2 years ago
When done this way (as the Myth Busters did with their car example) then when the plane moves forward, the treadbelt will speed up fast enough to match the plane's wheelspeed and create enough opposing force through the tires to cause the plane to have 0 airspeed.
Think about it....if the Mythbusters measured car's airspeed (like your plane interpretation) then the car would run off the end of the treadbelt!! Just think about it.
All I ask is consistency, then the results will be the same!
johnboozer 2 years ago
@jackdinn1975 The car's speed in relationship to the ground (under the treadmill) was 0. The Mythbusters did properly conduct the experiment. The airplane moved forward (relative to the Earth) at 20 mph while the conveyor belt moved backwards (relative to the Earth) at 20 mph. That's why the Mythbusters included teh cones as a point of reference. Your complaint demonstrates your own fundamental misunderstanding of the principles involved, not why they got it wrong.
minnaandjoe 3 months ago
whoever thought it wouldnt take off is dumb
McDonoughSP 4 years ago 2
I didn't think it would, but then, I thought they would test it correctly.
apocalypse121 3 years ago
"Move Forward" with the Car = Moves in relation to the treadbelt.
"Move Forward" with the Plane = Moves in relation to the earth.
Contradictory, to say the least.
johnboozer 4 years ago
the belt was moving 20mph in one direction, the plane was moving 20mph in the other direction. Same frame of reference, speeds were matched. Period.
mitchio83 2 years ago
But in the car's example, the belt moves 20mph in one direction...and the car goes 0mph in the other direction. Same reference, speeds were NOT matched!! Period.
Apples to Oranges my friend.
OR--"Vehicle's" speed is determined by reference to the surface upon which it is traveling. Belt = 20mph, airspeed = 0 mph, = plane does not fly.
(add as many 0's to the figures above, and the answer remains the same...NO FLY!!!!)
johnboozer 2 years ago
I understand your point with the car thing, but that does not change the fact that a conveyor belt going any speed cannot hold an airplane stationary.
mitchio83 2 years ago
@johnboozer An airplane, however, moves forward by pushing against the air. The engines are in no way connected to the wheels. The wheels are free spinning. Only wind affects an airplane's takeoff ability, not anything that has to do with the ground. Of course if the airplane's wheel speed matches the conveyor belt speed it won't move, but that would only happen if the wheel bearings were completely frictionless and the engine was off or at idle.
jetengine7 2 years ago
@johnboozer
That's not reality. As soon as the engine is producing enough thrust, the airplane will accelerate forward, even if the conveyor belt is spinning the wheels at a million rpm.
jetengine7 2 years ago