Fictitious forces do not appear in the equations of motion in an inertial frame of reference. In an inertial frame, the motion of an object is explained by the real impressed forces. In a non-inertial frame such as a rotating frame, however, Newton's first and second laws still can be used to make accurate physical predictions provided fictitious forces are included along with the real forces. For solving problems of mechanics in non-inertial reference frames, treat the fictitious forces like real forces and pretend one is in an inertial frame.