The runner is a non-inertial system, and it should be calculated with wide phase instead of narrow phase. I remember that in Shu Yousheng's grandfather's book Mechanics, there are many examples of inconsistency found through narrow-phase calculation. Then, the author explained to us which parts of these examples are beyond the range of narrow phase, and should be calculated with wide phase, and only the calculation of narrow phase will produce errors.

? In addition, if the research object does not involve the points on the wheel, you can actually use the special theory of relativity (of course, this question is not applicable). Generally, there are two ways to do it: the first way is the college entrance examination (scale reduction+clock slowness+clock misalignment), and all three effects should be considered at the same time. The second one is Lorentz transformation. This method has a wide range of applications and is convenient to calculate, but it is not suitable for second problems. There is no paradox, and the answer of quantitative calculation is obvious.

? Grab any point on the steering wheel and record it as an event at a certain moment. The point returns to the starting position in the circle and records it as an event. The spatial coordinates of the two events in the inertial system in the car are the same. According to Lorentz transformation, the coordinates of the two events in the ground inertial system are respectively and then enter. According to observation, the horizontal moving distance of the point is, and the distance that the point moves laterally is the distance that the vehicle moves, so the speed is the distance divided by the time interval.

do you know where you made a mistake? Do you remember the clock slow effect, but I forgot that there was also the scale contraction effect. In the car, the inertial road surface seems to move at a constant speed, so it is reduced. For two fixed points on the road surface, the distance measured is shorter than that measured on the ground by a proportional reduction factor (because the two fixed points on the ground are still in the inertial system relative to the ground itself).