think about this... - Page 44

d10 · #**431** 11-23-2005, 07:46 PM

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You've mentioned this five times now, and you've been right each time, but they're just not understanding what you're saying of course. The plane can take off, for all the reasons stated already, but when it does take off, the wheels will be moving x mph faster than the conveyer belt, where x=the plane's velocity relative to the ground/air/whatever.

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The wheels will only move as fast as the force spinning them. In this case the conveyor belt. Remember they are independent of the movement of the plane. The plane can move and the wheels can stay still. The wheels can move and the plane can stay still. Both can move independently at the same time (as in this case).

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Yes, they can, but the OP stated that they are not. It's like asking how long does it take a car to travel from point A to point B (where distance >0) moving at 0mph, and some people say it won't ever get there, but then other people say "OMG retard you can accelerate the car and then it will get there" and then the original people sit there scratching their heads wondering where the misunderstanding is.

LAGmaniac · #**432** 11-23-2005, 07:47 PM

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You've mentioned this five times now, and you've been right each time, but they're just not understanding what you're saying of course. The plane can take off, for all the reasons stated already, but when it does take off, the wheels will be moving x mph faster than the conveyer belt, where x=the plane's velocity relative to the ground/air/whatever.

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The wheels will only move as fast as the force spinning them. In this case the conveyor belt. Remember they are independent of the movement of the plane. The plane can move and the wheels can stay still. The wheels can move and the plane can stay still. Both can move independently at the same time (as in this case).

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How can the plane move and the wheels stand still?

#**433** 11-23-2005, 07:50 PM

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Yes, they can, but the OP stated that they are not. It's like asking how long does it take a car to travel from point A to point B (where distance >0) moving at 0mph, and some people say it won't ever get there, but then other people say "OMG retard you can accelerate the car and then it will get there" and then the original people sit there scratching their heads wondering where the misunderstanding is.

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I see your point, I think I just read the question as the OP intended it. A trick question of sorts. Then I missed the last couple of posts arguing about the intent of the OP.

#**434** 11-23-2005, 07:54 PM

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How can the plane move and the wheels stand still?

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The wheels do not move while the plane is flying. My point is forward movement of the plane is not driven by the wheels in any way, shape, or form.

lgas · #**435** 11-23-2005, 08:01 PM

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Good. Anyone who can't understand after thinking about the rollerskates on treadmill example or the stroller on moving walkway example is just a fool.

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The problem is that those two examples don't take into consideration the one condition from the OP:

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The runway moves in the opposite direction of the plane at the exact same speed as the plane's wheels.

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Neither the treadmill or the moving walkway would speed up/slow down to match the speed of the rollerskates/stroller.

Since much of the confusion in this thread seems to come from people's confusion as to whether the magical speed-matching conveyor belt from the OP somehow negates the ability of the plane to move forward, I don't think these examples with normal every day non-magical conveyor-belt-like devices are sufficient to make the solution clear to everyone.

Personally I think the problem comes from the magical conveyor-belt condition in that it couldn't possibly exist in real life. If somehow it did, I imagine what would happen is that the plane's forward velocity would exceed the rotational velocity of the wheels and the wheels would rip off... then the plane crash to the earth because it would not have acheived full take-off velocity yet... but the conveyor belt would've stopped moving at this point since the wheels would've stopped moving, so now the plane would go skidding off the magical conveyor belt on its belly onto the tarmac (or whatever surrounds the magical conveyor belt) and then the problem becomes reduced to whether the plane in question can take off with its landing gear up (or in this case, sheered off). I'm guessing most planes can't, but I don't really know for sure.

Edited for typos.

LAGmaniac · #**436** 11-23-2005, 08:14 PM

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How can the plane move and the wheels stand still?

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The wheels do not move while the plane is flying. My point is forward movement of the plane is not driven by the wheels in any way, shape, or form.

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Oh ok, I don't think anybody is having any trouble with that part. The issue is that it doesn't matter if the plane is moving the wheels or the wheels are moving the plane, (in fact neither is happening).

As the plane moves forward the wheels must move faster than the conveyor belt is moving, even if they are just being taken along for the ride.

Just like pushing a skateboard forward on a treadmill. The only time the wheel speed equals the treadmill speed is when you are holding the skateboard stationary.

Edit: To illustrate imagine the skateboard on a treadmill moving at 1m/s. After one second the wheel will have covered 1m of treadmill track.
Wheel speed 1m/s
Treadmill speed: 1m/s
Skateboard speed: 0m/s

If you push the skateboard forward during that second at a rate of 1m/s the wheel will have covered 2m of track.
Wheel speed 2m/s
Treadmill speed: 1m/s
Skateboard speed: 1m/s

Therefore in order for the skateboard to move forward, wheel speed must be greater than treadmill speed and the conditions of the OP can't be met.

jman220 · #**437** 11-23-2005, 08:59 PM

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I think (hopefully) everyone is beyond this point by now. The only question is, how retarded was the wording of the OP?

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- Riddle: does x + y = x?
- No.
- Yes it does! Just ignore y. Idiot.
- [img]/images/graemlins/frown.gif[/img]

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y = 0

duh

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You do realize that you just conceded to all of us that the airspeed is zero, and therefore the plane will not take off, don't you?

jman220 · #**438** 11-23-2005, 09:02 PM

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You've mentioned this five times now, and you've been right each time, but they're just not understanding what you're saying of course. The plane can take off, for all the reasons stated already, but when it does take off, the wheels will be moving x mph faster than the conveyer belt, where x=the plane's velocity relative to the ground/air/whatever.

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The wheels will only move as fast as the force spinning them. In this case the conveyor belt. Remember they are independent of the movement of the plane. The plane can move and the wheels can stay still. The wheels can move and the plane can stay still. Both can move independently at the same time (as in this case).

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Not the way the op was worded, no, this isn't true. And backpeddling 20 pages later when you realize that your Op is impossible and AFTER calling everyone who said the plane won't take off is idiots doesn't work. Are these magical wheels that are not attached to the plane? Becausee that is what you are asserting.

#**439** 11-23-2005, 09:10 PM

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Therefore in order for the skateboard to move forward, wheel speed must be greater than treadmill speed and the conditions of the OP can't be met.

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The only way I can explain my thought process is like this. Imagine there was no ground. Do we agree that if the plane were suspended in air somehow that it could still take off via engine/prop propulsion?

Now imagine that while the plane is taking off in mid-air some force (think the treadmill) was spinning the wheels at 1 MPH. The plane is now traveling at takeoff speed and the wheels can still be spinning at 1 MPH via this force. Take this further and imagine the treadmill coming along for the ride. Treadmill going backwards at x speed, wheels spinning forward at the exact same speed. Plane flying though air at y speed.

For all intents and purposes this is what the original scenario would be like but on the ground. To observers it would look like the plane was gliding along the treadmill. Wheels and treadmill both going the same speed in opposite directions.

Slow Play Ray · #**440** 11-23-2005, 09:11 PM

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I think (hopefully) everyone is beyond this point by now. The only question is, how retarded was the wording of the OP?

[/ QUOTE ]
- Riddle: does x + y = x?
- No.
- Yes it does! Just ignore y. Idiot.
- [img]/images/graemlins/frown.gif[/img]

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y = 0

duh

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You do realize that you just conceded to all of us that the airspeed is zero, and therefore the plane will not take off, don't you?

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no.

and please show me where someone was called an idiot.

actually, don't. this thread is getting stupid - it's all pride now. everyone understands the problem, the solution, and the "problem with the problem" - there is truly nothing more to discuss.