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Author Topic: Tire Speed!  (Read 1334 times)

Offline earl1937

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Tire Speed!
« on: May 07, 2013, 06:10:05 PM »
 :airplane: I am rolling out after landing in my B-17 and I am doing 20MPH, what is the speed of the part of the tire which is touching the ground doing in MPH?
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Offline Arlo

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Re: Tire Speed!
« Reply #1 on: May 07, 2013, 06:30:53 PM »
I think I've seen a version of this online already:

http://www.youtube.com/watch?feature=player_embedded&v=Qhm7-LEBznk    :D

(Ducks)  :bolt:
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Offline Karnak

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Re: Tire Speed!
« Reply #2 on: May 07, 2013, 06:33:11 PM »
Quote from: earl1937 on May 07, 2013, 06:10:05 PM
:airplane: I am rolling out after landing in my B-17 and I am doing 20MPH, what is the speed of the part of the tire which is touching the ground doing in MPH?
0mph.

If you stand on the brakes it will be doing 20mph, briefly.
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Offline RTHolmes

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Re: Tire Speed!
« Reply #3 on: May 07, 2013, 06:34:58 PM »
relative to what? </Einstein>
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Offline colmbo

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Re: Tire Speed!
« Reply #4 on: May 07, 2013, 07:02:32 PM »
Quote from: earl1937 on May 07, 2013, 06:10:05 PM
:airplane: I am rolling out after landing in my B-17 and I am doing 20MPH, what is the speed of the part of the tire which is touching the ground doing in MPH?

Indicated, calibrated, true or ground?
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Offline Arlo

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Re: Tire Speed!
« Reply #5 on: May 07, 2013, 07:14:29 PM »
Skidding or rolling?
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Offline mechanic

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Re: Tire Speed!
« Reply #6 on: May 07, 2013, 07:43:14 PM »
Two answers, the obvious one is 0mph. Although that is ambiguous because the part that is touching the tarmac is always changing.

The other obvious answer is 20mph, because the aircraft is moving at 20mph along with everything attached to it.

I'm guesing this is some kind of clever riddle and I am wrong twice.
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Offline Tank-Ace

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Re: Tire Speed!
« Reply #7 on: May 07, 2013, 08:15:38 PM »
You could also probably find an equation for the speed of any given point on the tire as it rolls along the ground, based on the radius...
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Offline BaldEagl

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Re: Tire Speed!
« Reply #8 on: May 07, 2013, 10:20:53 PM »
Quote from: mechanic on May 07, 2013, 07:43:14 PM
The other obvious answer is 20mph, because the aircraft is moving at 20mph along with everything attached to it.

Actually that speed would oscillate based on whether the particular part of the tire was moving forward over the top (faster than 20 mph) or rearward under the bottom (slower than 20 mph) equalizing at 20 mph in the horizontal plane.

If the question had been about a particular and constant point on the tire it would be much faster than 20 mph but we'd need the tire radius or diameter to calculate the speed.  As that information wasn't provided we can eliminate that answer.

The real answer is 0 mph for the portion of the tire in contact with the ground which was the question.
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Offline earl1937

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Re: Tire Speed!
« Reply #9 on: May 08, 2013, 04:16:58 PM »
Quote from: BaldEagl on May 07, 2013, 10:20:53 PM
Actually that speed would oscillate based on whether the particular part of the tire was moving forward over the top (faster than 20 mph) or rearward under the bottom (slower than 20 mph) equalizing at 20 mph in the horizontal plane.

If the question had been about a particular and constant point on the tire it would be much faster than 20 mph but we'd need the tire radius or diameter to calculate the speed.  As that information wasn't provided we can eliminate that answer.

The real answer is 0 mph for the portion of the tire in contact with the ground which was the question.
:banana: :banana: :banana: You sir, are correct, the part touching pavement is NOT moving! If it moved, it would be skidding or slipping! LOL
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Offline mtnman

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Re: Tire Speed!
« Reply #10 on: May 08, 2013, 08:10:12 PM »
Quote from: earl1937 on May 08, 2013, 04:16:58 PM
:banana: :banana: :banana: You sir, are correct, the part touching pavement is NOT moving! If it moved, it would be skidding or slipping! LOL

Is this with, against, or somewhat across the rotation of the earth?  That would have an effect on the speed of the part touching the ground, no?
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Offline BaldEagl

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Re: Tire Speed!
« Reply #11 on: May 08, 2013, 11:07:43 PM »
Quote from: earl1937 on May 08, 2013, 04:16:58 PM
:banana: :banana: :banana: You sir, are correct, the part touching pavement is NOT moving! If it moved, it would be skidding or slipping! LOL

Thank you for the accolades (if that's what dancing bananas are... which reminded me of this: http://www.allmedia.com.au/bananana/) but Karnak got it first.
« Last Edit: May 08, 2013, 11:12:38 PM by BaldEagl »
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Offline Motherland

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Re: Tire Speed!
« Reply #12 on: May 12, 2013, 05:26:50 PM »
see: physics I lecture 10 or so
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Offline Arlo

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Re: Tire Speed!
« Reply #13 on: May 12, 2013, 05:35:12 PM »
How fast are my spinner hubcaps moving when my tires are stationary on the rearm pad.  :D
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Offline Bino

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Re: Tire Speed!
« Reply #14 on: May 15, 2013, 10:23:58 AM »
Quote from: earl1937 on May 07, 2013, 06:10:05 PM
:airplane: I am rolling out after landing in my B-17 and I am doing 20MPH, what is the speed of the part of the tire which is touching the ground doing in MPH?

African or European?
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