From the perspective of the rotating frame, the additional force terms are experienced just like the real external forces and contribute to the apparent acceleration. The additional terms on the force side of the equation can be recognized as, reading from left to right, the Euler force − − m d ω ω / d t × × r , the Coriolis force − − 2 m ω ω × × [ d r / d t ] , and the centrifugal force − − m ω ω × × ( ω ω × × r ) , respectively. Unlike the other two fictitious forces, the centrifugal force always points radially outward from the axis of rotation of the rotating frame, with magnitude m ω ω 2 r ⊥ ⊥ , where r ⊥ ⊥ is the component of the position vector perpendicular to ω ω , and unlike the Coriolis force in particular, it is independent of the motion of the particle in the rotating frame. As expected, for a non-rotating inertial frame of reference ( ω ω = 0 ) the centrifugal force and all other fictitious forces disappear. Similarly, as the centrifugal force is proportional to the distance from object to the axis of rotation of the frame, the centrifugal force vanishes for objects that lie upon the axis.