Let's tie a rope on an object, then we swing the object around in a circle, then we start running forwards while continuing the swinging. (All velocities are relativistic) An assistant takes lot of pictures of us doing this stunt. Then finally we study the pictures. We will notice that the object is more probable to be found on the side where the velocity of the object is larger. (This effect is a result of relativistic addition of the linear and the circular velocities of the object) So we conclude the object spends a longer time on one side. From this we conclude that the force exerted on the object is smaller on this same side. (So that the the impulse (F*t) does not become too large) From the principle of relativity we can see that the rope does not feel any decrease of stress at any time. Question1: Why does the part of the rope that moves very fast not feel any decrease of stress? (Because of the high velocity, I guess) Question2: Why does the part of the rope near the center of the circle that does not move so fast not feel any decrease of stress?