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Old 5th Feb 2020, 17:26
  #67 (permalink)  
MichaelKPIT
 
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Relative to the runway that's precisely what I'm saying. The very bottom of the tyre tread is moving at 0kt relative to the runway with which it is in contact. If not it would be skidding. The axle, x feet up from the runway is moving forward, relative to the runway, at 100kt (in this example.) The top of the wheel, 2x feet up from the runway, is moving forward, relative to the runway, at 200kt. The whole complete wheel, as a component piece, is obviously traveling forward at 100kt, however it is rotating, so the top has a forward velocity (speed in a given direction) greater than the axle or the bottom, and while the bottom is in contact with the runway, and is not skidding, it has the same forward velocity as the runway, which is obviously 0kt.
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