Not logged in [
Login
-
Register
]
You Are Not Registered Or Not Logged In
Corsa Sport
»
Message Board
»
Off Day
»
Question for everybody
» Post Reply
Post Reply
Who Can Post?
All users can post new topics and all users can reply.
Icon:
Formatting Mode:
Normal
Advanced
Help
Andale Mono
Arial
Arial Black
Book Antiqua
Century Gothic
Comic Sans MS
Courier New
Georgia
Impact
Tahoma
Times New Roman
Trebuchet MS
Script MT Bold
Stencil
Verdana
Lucida Console
-2
-1
1
2
3
4
5
6
White
Black
Red
Yellow
Pink
Green
Orange
Purple
Blue
Beige
Brown
Teal
Navy
Maroon
LimeGreen
Message:
HTML is Off
Smilies are On
BB Code is On
[img] Code is On
[quote][i]Originally posted by Steve[/i] The Solution: Here are the keys to understanding this problem: The wheels of an aircraft are "free-wheeling". They do not provide propulsion, and therefore do not "push against" the action of the conveyor belt. The thrust for aircraft movement comes from jet engines or propellors... not the wheels. Therefore, the thrust being applied to the aircraft body is completely decoupled from how fast the wheels happen to be spinning. Thrust acts according to Newtons Third Law of Motion - every action has an equal and opposite reaction. The thrust of the engines is acting against the air. Because the wheels are free-wheeling and we have assumed zero friction at the hub, it follows that the conveyor belt, no matter how fast it is moving, CANNOT EXERT ANY FORCE on the aircraft with respect to forward motion! There is no force in our experiment that can oppose the thrust vector of the aircraft. If the conveyor belt cannot exert any relevant force on the aircraft, you can completely ignore it. Ergo, the aircraft takes off as if nothing unusual is happening. Addressing Some Common Arguments: 1) "The conveyor belt will cancel out any forward motion of the aircraft. The plane will not move at all." Short Answer: The belt has no way to exert force with respect to the forward motion of the aircraft. All it can do is make the wheels spin faster or slower. Long Answer: Your conditions are illogical. You claim that the aircraft will not move If the plane doesn't move, then the conveyor belt doesn't move either If the belt is not moving, then how is it cancelling any forward motion of the aircraft? 2) "The plane will remain stationary, but will lift into the air... thus taking off." Answer: This is an aerodynamic impossibility (assuming no wind), which should be obvious. 3) "But if you said the the conveyor belt matches the speed of the WHEELS, it wouldn't be able to take off." Short Answer: See Argument #1. Long Answer: Once again, your conditions are illogical. The conveyor belt can never "match" the speed of the wheels unless the aircraft does not move. With a tremendous thrust vector behind it with no opposing force, the aircraft will move. Once the aircraft begins to move, we enter into a paradoxical situation. X = Wheel Rotational Speed X = Conveyor Belt Speed, as per your conditions Z = Speed of Aircraft = Some non-zero positive number The equation is: X = X + Z, which is illogical. Example. The aircraft is moving 10mph (X = X + 10) with the wheels rotating at 10mph. Therefore, the belt must react and accelerate to 10mph. But now the wheels are rotating at 20mph... and so on to infinity. 4) "You can't just ignore the conveyor belt as you claim. Take this situation for example..." A guy is standing on the conveyor. He sees a plane moving forwards away from him at 10mph on the conveyor. He also knows that the conveyor itself is also moving at 10mph in a forwards direction. The total velocity of the plane in relation to the ground must be 20mph. If the conveyor can be ignored then why is the plane's total velocity twice what it would normally be if it was moving along on tarmac. The fact that you cannot explain this indicates that you've either ignored or overlooked some of the forces at play between the conveyor and the plane. I don't see any violations. You state that the aircraft is moving 10mph relative to the conveyor (perhaps as measured by a speedometer on the wheels). The conveyor itself is moving 10mph relative to the ground in the same direction. The total speed of the aircraft relative to the ground (tarmac) is 20mph. I don't see any problem with this. Ignore the conveyor by making it pop out of existence and you suddenly have an aircraft traveling down the tarmac at 20mph. You can change your point of view as much as you like, but you still end up with an aircraft traveling 20mph with respect to the ground. [/quote]
Post Options:
Disable smileys?
Turn BBCode off?
Receive email notification of new replies?
This is a long topic, click
here
to review it.