"There is no better example of the decline of education in this country than this thread."
Amen...
"There is no better example of the decline of education in this country than this thread."
Amen...
dmb wrote:
the plane remains stationary relative to the air surrounding it.
Bernoulli's equation shows that no pressure differential created, and hence no lift.
STFU.
If that is how you interpret the riddle (that there is no air speed) then you are 100% correct. The reason why this stupid "harmless" riddle has taken so much attention is because people are imagining different scenerios and, correctly, reach opposite answers.
Scenerio #1: The plane's stated "speed" is what the treadmill display would say, i.e., the speed of the belt, as the plane is stationary with respect to the air around it. This is the same as saying that a person is running 10 mph on a treadmill, in the usual case, that displays 10 mph on the console. The runner's airspeed is zero, as would the plane's airspeed in this scenerio and there would be no lift and thus no take off.
Scenerio #2: The planes's stated "speed" is airspeed and not what the treadmill says. The plane is free to accelerate on a very long treadmill according to the thrust of it's engines until reaching sufficient airspeed to create enough lift for take off; all the while the treamill's speed in the opposite direction is virtually negated by the near frictionless oiled berrings of the wheels.
Two prudent interpretations to same riddle that produce opposite results. The fellow who introduced this riddle to the board, knowing full well it wasn't "harmless", should either be shot or given the award for best troll.
David wrote:
"There is no better example of the decline of education in this country than this thread."
Amen...
Speaking of amen......
This riddle and thread reminds me of religion.
Somebody makes up a hypothetical story, different people interpret the story different ways even though there may not be a real answer to who is right.
All sides of the discussion become more impassioned, the discussion turns into an argument continues to escalate.
Maybe the catholics and protestants started out this way, or the sunnis and shiites?
The truth of the matter wrote:
David wrote:"There is no better example of the decline of education in this country than this thread."
Amen...
Speaking of amen......
This riddle and thread reminds me of religion.
Somebody makes up a hypothetical story, different people interpret the story different ways even though there may not be a real answer to who is right.
All sides of the discussion become more impassioned, the discussion turns into an argument continues to escalate.
Maybe the catholics and protestants started out this way, or the sunnis and shiites?
Hilarious.
turkey leg wrote:
Scenerio #1: The plane's stated "speed" is what the treadmill display would say, i.e., the speed of the belt, as the plane is stationary with respect to the air around it. This is the same as saying that a person is running 10 mph on a treadmill, in the usual case, that displays 10 mph on the console. The runner's airspeed is zero, as would the plane's airspeed in this scenerio and there would be no lift and thus no take off.
Two prudent interpretations to same riddle that produce opposite results.
Except Scenario #1 isn't really a prudent interpretation because it violates a few pesky laws of physics.
not again wrote:
turkey leg wrote:Scenerio #1: The plane's stated "speed" is what the treadmill display would say, i.e., the speed of the belt, as the plane is stationary with respect to the air around it. This is the same as saying that a person is running 10 mph on a treadmill, in the usual case, that displays 10 mph on the console. The runner's airspeed is zero, as would the plane's airspeed in this scenerio and there would be no lift and thus no take off.
Two prudent interpretations to same riddle that produce opposite results.
Except Scenario #1 isn't really a prudent interpretation because it violates a few pesky laws of physics.
Not to mention that a plane is generally not powered by it's wheels... Something necessary for scenario #1 to work.
I'm curious why some want to add complex variables to the original riddle. The riddle states that the plane is sitting on a treadmill, not a runway length treadmill. Why would anyone presume that the treadmill is any longer than the plane?
Not that it matters to the "plane won't fly" crowd, I guess that youtube vid proving the plane will take off must be some kind of fake, or heresy, or worse yet black magic...
I'll post this again. It's not my answer (found it on a different thread) but it is unarguably an elegant and valid explanation.
"Get your roller blades (Perfect Physics rollerblades...no friction in the wheel bearings) and go over to the gym. Put on the skates and hop on a level treadmill. Turn on the treadmill.
No matter how fast the treadmill is spinning, you won't go anywhere - the wheels spin at the same speed as the treadmill surface and you stay at 0mph with respect to the fixed floor.
In other words, it's EXACTLY like you were standing on a smooth, frictionless surface. Play with the treadmill speed all that you want, it makes no difference, you don't move. There is NO FORCE causing you to move backward. Set the treadmill to 1mph or 100mph, you don't go anywhere, even though the skate wheels will be spinning like mad.
Now let's apply some forward thrust. Your buddy comes up behind you, standing on the floor, and starts to shove you forward. You begin to move up the treadmill at exactly the speed he is pushing. If he pushes you at 1mph, you move at 1mph, even though you've got the treadmill moving at 100mph.
And that's exactly what happens with the airplane on the conveyor belt - it's just a plane on a frictionless runway. The jet engine provides thrust which causes forward motion regardless of how slippery the runway is. The wheels can revolve at 1mph, 100mph or 1000mph, it makes no difference at all."
Therefore ... assuming the treadmill is as long as a runway (and why not since the riddle is hypothetical) the plane will take off.
Please tell me you're referring to the "plane can't take off" crowd.
Otherwise you'd be that example
This thread verifies the bell curve.
Everything you sad is correct. However, nothing will matter to the other side. This is not a debate, the plane will take off,
regardless of runway length, wheel speed, etc..
The religion example is great, any good fundamentalist knows that life doesn't evolve, that dinosaur bones were put there by the devil to tempt our faith in creation.
Try reasoning with that.
WAIT WAIT WAIT wrote:
If the wheels are touching the treadmill, the plane cannot move forward unless wheel speed is greater than treadmill speed. The origin of the force does not change this fact.
Yes - the wheel speed must be greater than the treadmill speed. But, the riddle says that the treadmill speed matches the PLANE speed. Please google how a plane's speed is measured. I'll give you a hint - it sure as hell ain't done by the wheels.
The problem is that a treadmill CANNOT keep a plane in place.
Here is another experiment similar to the string - but slightly different.
The next time you go to an airport bring a friend, a broomstick, and some roller blades. Go to one of those conveyer belts that speed up your walk. Now let's pretend that it's late at night and nobody is there to disturb you.
You are going to do an experiment to show how it does make a difference where force is applied for a treadmill to keep something in place.
1)Put on the roller blades. Then have your friend walk onto the "wrong" end of the conveyer belt (the belt is running towards him). Have him hold one end of the broomstick while you hold on to the other end. He will walk or run so that he is moving faster than the treadmill so that he can pull you on. Once you are on he will walk at a certain pace so that both of you stay stationary in comparison to the ground and air.
2)Keep your roller blades on. This time you will be beside your friend. You will enter the conveyer belt, but he will walk beside the conveyer belt - both of you holding onto the broomstick. He will walk at the same pace as he did in the first situation on the conveyer belt when he kept you both stationary in relation to the ground. You will note that this time however that since the conveyer belt is not in contact with where his force is applied (his feet) that he will move forward in comparison with the ground and so will YOU! The only difference is that your wheels are spinning faster. If he walks forward at any pace - than both of you move forward in comparison to the ground. The conveyer belt is powerless to counteract any of his force.
This is the same reason why the plane cannot be kept in place by the treadmill. The force of the engines is acting on the air - and the treadmill can't do anything to effect the air. Therefore the plane must move forward if any thrust is applied by the engines.
Neb - In some places, the riddle is stated as wheel speed = treadmill speed. On letsrun, it was plane speed = treadmill speed. I agree with other numerous posters that in the former scenario, the plane does not take off; in the latter, it does.
the postdoc guy that posted on the previous page of this thread had a good post that people seem to have ignored. I actually think he or she might have a PhD, unlike the other "professors" and "aerospace engineers" posting on this thread. Nice post.
The only place i've seen the riddle stated as "wheel" speed is boingboing - which has a link at the top of the page to an explanation of the riddle that states it should be plane speed - and that anyone who states it as wheel speed has the riddle worded incorrectly.
Can you answer how a treadmill would keep a plane in place that is powered by engines through the air?
With all the arguments about war, religion, and politics in this world - can't we agree on one thing? That a giant treadmill cannot keep an airplane stationary to the air around it?
; )
Neb, you need a nice helping of STFU.
im not saying your wrong because you are right the plane takes off. but you are the most annoying person in the world and you are saying the samething in 50 different posts. the dumb are exactly that DUMB, and they cannot be swayed this is the same reason why bush got re-elected. so please do us all a favor and shut the hell up because a smart person who was tricked by the riddle at first(myself as an example), understood it by page 2 which you arent even on. BTW 99% of the it wont takke off folk are trolls and you are getting WTFBBQSAUCE PWNED by them and in general sounding like a 2 year old yourself.
have a nice day <3
I'm going to steal a few poster's points and add to them to settle this once and for all. The basic final answer is that the question is flawed and there isn't a correct answer.
So read this.
Original Riddle.
"An airplane is sitting on an enormous treadmill. As the plane starts its engines, the treadmill runs in the opposite direction at the same speed the plane is moving. Can the plane take off?"
I've spent much time mulling this over, and I'm confidant I've finally come up with the correct answer. Read carefully and slowly, and maybe read it a couple times to get the whole picture. Then tell me if you think i'm wrong...because I'm right.
1. The argument that the plane takes off is predicated upon the plane moving forward through the air.
2. For the plane to move forward through the air, it is necessary for the plane's wheels to be moving faster than the treadmill.
3. If the treadmill's speed matches the plane's wheels, the plane does not move forward through the air and the plane does not take off.
Now I totally understand the "free spinning wheel" defense...because air is stationary and that's what the engines are pushing against, they aren't pushing against the treadmill, so the plane would move forward on the treadmill and create air flow, thus producing take off....but that would then make the plane go faster than the treadmill (see point 2) which is against the rules of the riddle.
So in hindsight...this riddle is bogus,it poses a question that really isn't possible. When the engines come on (as it states in the riddle) there would be no way for the treadmill to be going the same speed in the opposite direction, because they are pushing against different forces(air/ground). This would be like saying 2 + apple is what? Right.... So I think we're all wrong because it's a bogus question.
The riddle is not bogus. The plane takes off. Get over it. Don't take my word for it either.
http://youtube.com/watch?v=-EopVDgSPAk
http://www.straightdope.com/columns/060203.html
The plane can go the exact speed as the treadmill and take off because it's wheels spin @ twice the planes speed.
x = planes speed
-x = treadmill speed
2x = wheel speed
2x - x = x (result is net postive speed, plane flys)
who measures the speed of a plane by the speed of the wheels of the plane?
Mother, please make it stop! (Not the plane, the discussion.)
"2 + apple is what? Right..."
Well when the plan is on the ground, or in this case a treadmill...then I'd measure it's speed by the wheels...but when it's in the air I'd measure it by airspeed.