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Thread ID: 64128 2005-12-04 07:01:00 Sunday night Brain Bender - Airplane Physics miknz (3731) PC World Chat
Post ID Timestamp Content User
409982 2005-12-04 10:53:00 The plane will not take off.

If you could anchor the plane to the runway with a long rope out behind, put the engines on full steam ahead, would the plane leave the ground. NO.

If it did they would be using this method for plane take off now, less tyre wear, less use of the runway etc.

imagef1.net.nz

0/10 for you as well. 		Safari (3993)
409983 2005-12-04 10:56:00 Another thought, the plane would have to be anchored otherwise the plane would move forward, regardless of how flash the conveor belt was.

The wheels just keep the belly of the plane proped off the ground.

So unless the plane was anchored it would zoom off down the runway and take off like normal. 		Rob99 (151)
409984 2005-12-04 12:22:00 Okay, that was a bit of a trick one.

Yes, the plane will take off. Even though the wheels are matching the speed of the conveyer, its the thrust (the reaction between the engines/prop/jets/whatever and the air) that will be propelling the plane forward. Those wheels would be rotating at a hell of a speed by the time the plane got enough lift to take off though. The wheels/conveyer thing is a bit of a red herring.

If the conveyer was moving in the takeoff direction, at the right speed and rate of acceleration, it is conceivable that the plane could lift off without the wheels revolving at all. I think... 		Catweazle (2535)
409985 2005-12-04 12:45:00 If the conveyer was moving in the takeoff direction, at the right speed and rate of acceleration, it is conceivable that the plane could lift off without the wheels revolving at all. I think...Correct. Rob99 (151)
409986 2005-12-04 16:25:00 On a second thought, I think the plane would not be able to take off. This is because its forward velocity is canceled out by the conveyor belt, therefore no air flow would be able to pass through the wing, which means no upward thrust would be provided.

Cheers :)

100% correct 		JJJJJ (528)
409987 2005-12-04 16:28:00 :D

The score so far:

pine-o-clean 10/10

greg 10/10

BM 10/10

gibler 10/10

Terry Porritt 10/10

drcspy 0/10 but full marks for Bernouli knowledge of differential pressure over an aerofoil.

JJJJJ 0/10 shame on you being a pilot.

JamesKan 0/10

Lagbort 0/10

Now I'm going laughing to bed and hope I can get to sleep :)

100% wrong 		JJJJJ (528)
409988 2005-12-04 16:31:00 The plane will take off, the only difference being that the wheels will be rotating at something like twice the speed. (conveyor -100 knots, aircraft driven by jet or propellors +100 knots, wheel rotation speed equivalent to 200 knots.)

Cheers

Billy 8-{)

The wheels would not be turning. They would be sliding. Equal force in both directions 		JJJJJ (528)
409989 2005-12-04 17:21:00 Liken the question to a person walking on a treadmill. If your walking speed equals the treadmill speed then you are just going up and down in the same place.
The same with our mythical aircraft. Equal and opposite forces do not create motion.
To leave the ground you require airspeed. Airspeed is created by ground speed. You also get a little airspeed from propeller wash, but not enough.
Bring a ,say, 40 knot headwind into the equation and you would leave the ground.
It is not uncommon to see a light aircraft tied down but with wheels off the ground 		JJJJJ (528)
409990 2005-12-04 17:38:00 Liken the question to a person walking on a treadmill. If your walking speed equals the treadmill speed then you are just going up and down in the same place.
The same with our mythical aircraft. Equal and opposite forces do not create motion.
To leave the ground you require airspeed. Airspeed is created by ground speed. You also get a little airspeed from propeller wash, but not enough.
Bring a ,say, 40 knot headwind into the equation and you would leave the ground.
It is not uncommon to see a light aircraft tied down but with wheels off the ground

You are not thinking about the problem logically Jack.
The spinning wheels are not producing any force on the aircraft.
Have a read here it might clarify things
www.avweb.com 		Safari (3993)
409991 2005-12-04 18:23:00 It is more than obvious that it would take off. No problemo.

But the real question is...

Can we afford to buy a ticket after air newzealand has added in all the extra charges ;)

conveyer tax,etc.... 		Nyuuji (5460)
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