Final answer:
The velocity of an object in one reference frame relates to another moving frame through relativistic transformations, simplifying to classical addition at low speeds but requiring Lorentz transformations at high speeds.
Step-by-step explanation:
The relationship between the velocity (u) of an object as measured in a stationary reference frame and the velocity (u') as measured in a frame moving at velocity v is given by the relativistic transformation of velocity. At low velocities, the term vu' / c² becomes very small and the formula u = (v + u') / (1 + vu' / c²) simplifies to the classical velocity addition, u = v + u'. However, for high-speed scenarios where the velocities are a significant fraction of the speed of light, the effects of special relativity must be considered, leading to corrections as described by the Lorentz transformation equations. These transformations are necessary to ensure the consistency of the speed of light in all inertial frames of reference.