where the angular acceleration term is zero for the constant rate of rotation. Because the first term, which is Ω Ω × × ( Ω Ω × × ( X A B + x B ) ) , is of the same form as the normal centrifugal force expression: Ω Ω × × ( Ω Ω × × x B ) , it is a natural extension of standard terminology (although there is no standard terminology for this case) to call this term the "centrifugal force". Applying this terminology to the example of a tube in a centrifuge, if the tube is far enough from the center of rotation, | X AB | = R ≫ | x B |, all the matter in the test tube sees the same acceleration (the same centrifugal force). Thus, in this case, the fictitious force is primarily a uniform centrifugal force along the axis of the tube, away from the centre of rotation, with a value | F fict | = ω R, where R is the distance of the matter in the tube from the centre of the centrifuge. It is the standard specification of a centrifuge to use the "effective" radius of the centrifuge to estimate its ability to provide centrifugal force. Thus, the first estimate of centrifugal force in a centrifuge can be based upon the distance of the tubes from the centre of rotation, and corrections applied if needed.