Plane on a Conveyor Belt

[TourSpoon]

Nope, it would not take off and I wouldn't approve of that setup. However, that has nothing to do with this question. The plane is on a conveyer belt, not stuck in the ground with pegs. Two totally different situations.

Then someone better blow up the co-pilot...then it will take off.

Speaking of Take off weren't there a couple of Canadians that used to say, "Take Off Hoser"!? They weren't talking about planes unless it was a beer plane.

[mikelz]

Haha wow, I haven't been on this forum since last season and I come back to find a topic on one of my loves of life, flight!

Thanks for the post. I think I'm coming around.

Does your analogy help me understand "air speed" versus "ground speed"? I hope so because that one baffles me.

[YogiTKE]

Myth Busters proved the plane will take off.

[mikelz]

Myth Busters proved the plane will take off.

Myth Busters is cute but I don't watch it all of the time.

They have they proven lots of stuff like whether or not a jet engine can blow a car over. I forget the outcome but they proved you can use a lot of jet fuel for 21 of minutes of programming. I was hoping to understand the physics.

[iacas]

Thanks for the post. I think I'm coming around.

Not sure what's hard to understand there...

If a plane requires 50 MPH air speed to take off, if you blow a 50 MPH wind at it, the plane could hover above the ground, effectively "gliding in place." (of course, no wind is that steady nor are there any pilots that can react so quickly as to stay exactly in line with changing wind speeds, so the plane would be going up and down, back and forth...). That's why planes prefer to take off into the wind - they can reach higher air speeds in shorter runway distances because they're already starting out at the wind speed (+10, +20, whatever).

[iacas]

Myth Busters is cute but I don't watch it all of the time.

Maybe you should have watched the "Plane on a Conveyor Belt" episode before commenting on it. The physics are fairly simple and were covered.

Heck, here's the physics for you in a very simple sentence: "Planes don't move forward like cars do." If you can't grok that sentence and understand why the plane takes off (fairly normally), perhaps there's very little hope for you.

[YogiTKE]

The plane will take off at the same speed no matter if it's on a conveyor or not. The speed of the conveyor has no bearing on the plan taking off since it's spinning free moving wheels. The propeller pulls the plane along unlike an engine rotating tires.

[JeffG]

Thanks for the post. I think I'm coming around.

Well, there are very different types of airspeed, indicated, calibrated, true...etc...

Bascially, airspeed is the speed of which you are moving through the fluid that is air. Groundspeed is, well...ground speed...the speed at which you are moving relative to the ground. Think of a boat. If the boat is set on 10mph, it's moving through the water at 10mph...so it's "waterspeed" (aka airspeed) is 10mph. If he's on a lake with no wind, his groundspeed and his "waterspeed" are identical. Now, stick the boat in a river going WITH the current, and say the current is moving at 10mph relative to the shore. Well, his waterspeed is still 10mph, but the current is 10 mph, so he's groundspeed is 20mph. Have him going upstream, and they cancel each other out, he's still going 10 mph through the water but people are laughing at him on teh shore b/c he isn't going anywhere. Same principle with airspeed. In fact, when I used to instruct back at the university, i'd take a student up and demonstrate it on a very windy day. Go up to about 5 or 6 thousand feet, find the direction of the wind and stick the nose into it. Drop the flaps, slow it down, and we could get a groundspeed of about 5kts if we wanted to (off the GPS). If wind was high enough we could even get a negative ground speed or even move backwards while still maintaining flight. So, even though we were moving through the air at 45-50 kts, that little tree down there wasn't moving at all relative to us.

[JaY_B]

Regardless of how little sense it might make, the plane takes off. Deal with it

[Pinseeker81]

Dang it you people are making me miss flying. I quit doing it cause I was getting married and $800 a month (which was only about 1.2 hours a weekend) was better used for....eating and stuff. Man I miss it so

[winders]

Folks,

The bottom line is that this is a trick question. Kind of like asking if England has the 4th of July....

It so simple it stupid.

Here is the text again:

A plane is standing on a runway that can move (some sort of large conveyor belt). The plane moves in one direction, while the conveyor moves in the opposite direction. The 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 take off?

The conveyor belt does not start moving until the plane does. So the plane has forward momentum as the belt starts moving. This is not important really but it makes things more clear.

Keep in mind that the wheels roll and have very little wheel bearing friction. The plane is pulling itself forward through the air, not by pushing off the conveyor belt. Re-read that sentence again.

Assuming the wheel friction is normal, the plane will accelerate as it pulls itself forward through the air and will take off just fine. But the wheels will be spinning twice as fast as the plane is traveling right until take off.

The trick part of the question is that it is posed in a way that makes you think the conveyor belt will prevent the plane from moving forward. That is not the case.

Another way to look at the problem that might make it easier to understand.:

Build a 20 foot conveyor belt system that is 12 feet high on one end and 2 feet high at the other. Build it with 6" high walls. Build it so these walls have sensors that can determine how fast as object is moving from top to bottom and can adjust the belt speed accordingly.

With the conveyor system on, get a skateboard and put at the top and let go of it. What happens? It rolls down the belt to the bottom. Why? The acceleration force of gravity is greater than the friction in the bearings.

S-

[srjorion]

Oh winders, you have resurrected the beaten dead horse!!!!!

You are 100% correct though

[DirtCheap]

Yep.. It's all about propulsion.
If you get propulsion from your wheels, a conveyor belt will stop you.
If you get it from anywhere else, a converyor belt has *almost* zero (**affect/effect) on you.


** I never have figures out the difference between these two..

[golf hungry]

yes it will

[Eore]

so this thread still drags on

they did it on mythbusters. it flew.

conversation over ;)

[Voiceontapex]

so i saw this question and being the dumb one i am i went and got a kite and got on the treadmill and started running, my mom walks in and asks me what im doing and I honestly couldnt come up with a sane answer 'trying to run as fast as i can to make this kite fly" but now i realize they are completely not the same thing HAHAHAHAHA

and after further reading i think of the conveyor belt as an everlasting runway so therefore it makes sense to me now

a 100 ft conveyor belt runway is the same as a 200 million mile and more runway

[winders]

and after further reading i think of the conveyor belt as an everlasting runway so therefore it makes sense to me now

Voiceontapex,

If you think the runway is any longer than it actually is, you don't get it. S-

[winders]

To add to my last post:

If anything, the runway is effectively shorter because of the increase in frictional drag in the wheel bearings. In other words, the forward thrust of the propeller(s) has to overcome that additional wheel bearing friction. It's not much, but it's there....

S-