Suppose that we have a bar of finite length which is rotating about its center of mass at a constant angular velocity in a horizontal plane. Gravity is neglected.
The fact that the bar stretches outwards is supposedly explained by the centrifugal effect i.e. the presence of a centrifugal force which acts radially (outwards) on the bar's constituent particles. However what concerns me is the fact that this force is only supposed to be present in a rotating reference frame, which suggests that if I observe a rotating bar in an inertial frame, I should not witness any elongation at all, which is obviously false. So if I am in an inertial frame, how am I supposed to explain the elongation of the bar?