According to Newton's First Law of Motion, an object in uniform motion is in an inertial frame of reference, just like an object at rest. The physical laws governing the motion of the coin (kinematics under gravity) remain the same in all inertial frames .

When the elevator is stationary or moving with uniform velocity (constant speed in a straight line), the acceleration of the elevator is zero ($a_{lift} = 0$). In both cases, the relative acceleration of the coin with respect to the elevator floor is equal to the acceleration due to gravity ($g$). Since the height ($h$) and relative acceleration ($g$) are unchanged, the time taken to reach the floor is the same in both cases ($t = \sqrt{2h/g}$) .