View Poll Results: what do you think?
Hoss is da man, no
25
33.78%
Geico's question. He knows, yes
42
56.76%
your both wrong its a vto
7
9.46%
Voters: 74. You may not vote on this poll
will the plane fly?
Registered User
Joined: Jan 2004
Posts: 138
Likes: 0
From: Maine
Originally Posted by rac156
I can't believe I just joined a forum to argue the physics of an airplane taking off from a conveyor belt. I must lead an exciting life.
Anyway to the question at hand:
The part of the question I believe to be tripping people up is "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation."
We all know that this is impossible but for the sake of the question assume it is true. Also assume there is no slip between the wheels and conveyor and the conveyor always travels in the opposite directon of the wheels. The speed of the aircraft relative to the ground is equal to the speed of the wheels minus the speed of the conveyor. If the plane is to have a forward velocity then there must be a difference between the conveyor speed and the wheel speed. If the plane is to take off the difference must be equal to or greater than the take off speed. Given the problem statement "the conveyor belt is designed to exactly match the speed of the wheels" the difference in the two must be zero therefore there will be no ground speed. If there is no ground speed there is no lift. The plane will not take off.
As for the plane on skis argument, if you make the same assumption of zero slip they wouldn't take off either. The fact that the skis slide on the surface allows the plane to accelerate and eventually take off.
Anyway to the question at hand:
The part of the question I believe to be tripping people up is "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation."
We all know that this is impossible but for the sake of the question assume it is true. Also assume there is no slip between the wheels and conveyor and the conveyor always travels in the opposite directon of the wheels. The speed of the aircraft relative to the ground is equal to the speed of the wheels minus the speed of the conveyor. If the plane is to have a forward velocity then there must be a difference between the conveyor speed and the wheel speed. If the plane is to take off the difference must be equal to or greater than the take off speed. Given the problem statement "the conveyor belt is designed to exactly match the speed of the wheels" the difference in the two must be zero therefore there will be no ground speed. If there is no ground speed there is no lift. The plane will not take off.
As for the plane on skis argument, if you make the same assumption of zero slip they wouldn't take off either. The fact that the skis slide on the surface allows the plane to accelerate and eventually take off.
Thread Starter
Registered User
Joined: Mar 2004
Posts: 3,988
Likes: 7
From: Nebraska
Originally Posted by Chrisreyn
Have any of y'all thought about how hard Geico is laughing at all teh uproar and arguement this silly question has stired up????
Actually this is quite interesting.
Registered User
Joined: Dec 2003
Posts: 896
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From: Minnesota
OK, one more post on this one...
why do planes have turbines or engines to drive a compressor or propeller, when apparently they should be driving the wheels underneath the plane? how does that power get transferred to the wheels?
i work for this company...Cirrus Design
why do planes have turbines or engines to drive a compressor or propeller, when apparently they should be driving the wheels underneath the plane? how does that power get transferred to the wheels?
i work for this company...Cirrus Design
Registered User
Joined: Jan 2004
Posts: 138
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From: Maine
Originally Posted by rac156
not true, plane speed is independent of wheel speed ONLY if there is slip between the wheel and the surface it is touching. In my statement previously I said to assume zero slip.
Registered User
Joined: May 2005
Posts: 1,060
Likes: 1
From: Peoria, IL
Originally Posted by Tengu
When the plane engines start thrusting the thing that moves is the PLANE; it does not have ANY effect on the wheel speed.
Take a toy car. Put it on a sheet of paper. Have someone slowly pull the piece of paper backwards (hold the car in place with your finger). Watch how fast the tires rotate. Now push on the car with your finger so the car moves ahead slowly. Do the wheels speed up? Yes. Now try to get the car to move forward without speeding the wheels up.
This thread is getting old. I'm pretty sure people are going to believe what they want to believe.
Registered User
Joined: Nov 2005
Posts: 0
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From: Iowa
People will believe what they want to believe. I just like for people to believe what is right. 
Lets look at it like this
the plane throttles up and begins to move forward. As a result of the plane moving forward the wheels turn (not as a result of being driven). The instant the plane moves the conveyor matches its motion in the opposite direction thus canceling forard progress. The pilot gives it more throttle and the plane again moves forward slightly and the wheels speed up. Again the conveyor instantly matches the speed and cancels forward progress. This pattern would continue and thus the plane would never gain ground speed as the conveyor is pusing it back as fast as it is trying to go forward.
given the same conveyor a sailboat on wheels would never move for the same reason as above.
Lets look at it like this
the plane throttles up and begins to move forward. As a result of the plane moving forward the wheels turn (not as a result of being driven). The instant the plane moves the conveyor matches its motion in the opposite direction thus canceling forard progress. The pilot gives it more throttle and the plane again moves forward slightly and the wheels speed up. Again the conveyor instantly matches the speed and cancels forward progress. This pattern would continue and thus the plane would never gain ground speed as the conveyor is pusing it back as fast as it is trying to go forward.
given the same conveyor a sailboat on wheels would never move for the same reason as above.
Thats MR Hoss to you buddy!
Joined: Jul 2001
Posts: 2,759
Likes: 3
From: Central Texas
No, it wouldn't be the same. The force applied to the plane by the string would be in a different direction than the force applied to the plane by the conveyor.
As a side note, that would take one VERY strong string.
As a side note, that would take one VERY strong string.