Two strange questions
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Carpenter Local 745
Joined: Apr 2006
Posts: 5,794
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From: on da beach
Two strange questions
1. How come the outside (tire) of a bike wheel in motion looks like it moves faster than the hub?
2. Does the air inside a wheel/tire in motion rotate with the wheel/tire assembly? or does the air stay stationary?
3. Would another question in this post be one to many?
Happy new year.
2. Does the air inside a wheel/tire in motion rotate with the wheel/tire assembly? or does the air stay stationary?
3. Would another question in this post be one to many?
Happy new year.
Posting Guru
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From: Valley of the Sun AZ
1. It is, the hub will rotate at a slower rate than the outer rim. Think of a helicopter. Physic states it could go faster, but the speed of the blade is almost supersonic and thus it if were to reach supersonic speed at the tip and non-supersonic at the hub it would delaminate.
2. Air in the tire will "move" with the tire, but there will be some lag. There are some areas which will cause it to move, but it is realtive to the tire. Does the air in your truck move when you drive with your windows open?
Yes, I realize I need to get a life….
2. Air in the tire will "move" with the tire, but there will be some lag. There are some areas which will cause it to move, but it is realtive to the tire. Does the air in your truck move when you drive with your windows open?
Yes, I realize I need to get a life….
i ain't rite
Joined: Mar 2005
Posts: 65,455
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From: Marlboro Mental Hospital.
well, since the title of this thread is 2 strange questions, and the body of the thread has 3 strange questions in it, the third strange question cancels out the first 2 strange questions, making the whole thread cancel itself out, so there is no need for any answers.
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Carpenter Local 745
Joined: Apr 2006
Posts: 5,794
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From: on da beach
Originally Posted by BIGKEN
Tom...you hit the nail on the head!!! No answers necessary!!! 
No need to answer.
As far as rotation goes - doesn't the end of the blade move at the same rpm as the hub section?
I remember watching a honey bee follow someone while the person was riding in a boat. (I was on the boat too) so the honey bee must have bee trying hard to keep up.
I guess air does move in an airplane, but the plane is not rotating.
Still kicking!!
Joined: May 2003
Posts: 6,061
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From: Kalispell, Mt.
On the outside of the wheel...the tire IS moving faster than the hub, technically. They are both turning the same revolutions per minute, but the farther away from the hub, the mass has to move faster to keep up with the center mass.
One way to test this.
You get a volunteer.
Then you describe a small circle on the ground and tell him, "I'm going to run around this circle."
Then walk ten steps out from that circle. Position your happy volunteer there and walk back to your smaller circle.
Now, you tell your friend to run along with you, but the mandate is he needs to keep even with your right shoulder...he cannot fall back...nor can you run as fast as possible...(or he'll kill ya!)
After about two or three laps... are you puffing and panting like he is? Did he have to run faster, to keep in the same position on your right side?
Now...while y'all run outside and try it out..I'll exit stage left, so I don't have to hear your volunteer beating you up for making him run so fast.
One way to test this.
You get a volunteer.
Then you describe a small circle on the ground and tell him, "I'm going to run around this circle."
Then walk ten steps out from that circle. Position your happy volunteer there and walk back to your smaller circle.
Now, you tell your friend to run along with you, but the mandate is he needs to keep even with your right shoulder...he cannot fall back...nor can you run as fast as possible...(or he'll kill ya!)
After about two or three laps... are you puffing and panting like he is? Did he have to run faster, to keep in the same position on your right side?
Now...while y'all run outside and try it out..I'll exit stage left, so I don't have to hear your volunteer beating you up for making him run so fast.
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Logistics Pro
Joined: Nov 2004
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From: Southern MD
Just like when Jimmy Stewart portrayed Charles Lindbergh.
He was flying along, having made all of these calculations, etc., etc.
He notices a fly in the cockpit of 'The Spirit of St. Louis'.
He told the fly to get out, that the weight had been calculated down to the 'nnnnnttttttttth' degree.
Now, he started to think.
IF the fly was flying around in the cockpit, did the airplane weigh more, or, just when the fly was sitting?
He was flying along, having made all of these calculations, etc., etc.
He notices a fly in the cockpit of 'The Spirit of St. Louis'.
He told the fly to get out, that the weight had been calculated down to the 'nnnnnttttttttth' degree.
Now, he started to think.
IF the fly was flying around in the cockpit, did the airplane weigh more, or, just when the fly was sitting?
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Posting Guru
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From: Valley of the Sun AZ
Originally Posted by khadma
As far as rotation goes - doesn't the end of the blade move at the same rpm as the hub section?
I guess air does move in an airplane, but the plane is not rotating.
I guess air does move in an airplane, but the plane is not rotating.
Yes, the plane can rotate, but most people do not like that....I do
I was meaning that when you are sitting in an airplane waiting for take-off you do not feel the air hit you when they accelerate down the runway. The air is moving is not just from the point it is not where it started out.
Slow day in Hawai’i?
Postmaster
Joined: Aug 2004
Posts: 4,004
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From: North of Boston MA
Originally Posted by Aztrainer
Technically yes, but the RPM is at the hub of the rotor and not at the blade tip.
Want to really make your brain work - try to figure out what the speed of the contact patch of a tire is. Is it the same as the speed of the vehicle? Or is it zero at the very point where rubber meets road?
I have one more strange question.....if you have a plane on a treadmill.....
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Joined: Mar 2003
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From: Northeast Wisconsin
Originally Posted by Nitramjr
Want to really make your brain work - try to figure out what the speed of the contact patch of a tire is. Is it the same as the speed of the vehicle? Or is it zero at the very point where rubber meets road? .....
Posting Guru
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From: Valley of the Sun AZ
Originally Posted by Nitramjr
I must be misunderstanding you...I hope. The angular velocity (rpm, °/sec, radians/sec, etc. ) of the tip of the blade is identical to that at the dead center of the hub - it has to be, even in a flexible assembly. The actual velocity through the air is much faster at the tip than at the hub - because it is travelling a much further distance in the same amount of time as Fordlover described.
Want to really make your brain work - try to figure out what the speed of the contact patch of a tire is. Is it the same as the speed of the vehicle? Or is it zero at the very point where rubber meets road?
I have one more strange question.....if you have a plane on a treadmill.....
Want to really make your brain work - try to figure out what the speed of the contact patch of a tire is. Is it the same as the speed of the vehicle? Or is it zero at the very point where rubber meets road?
I have one more strange question.....if you have a plane on a treadmill.....
AND OH NO YOU DID NOT>>>>>>>>>>>>>