Methods and apparatus for weighing an article, such as a mail piece, while the article is moving, for example along a transport path (FIG. 2). In one embodiment, a weigh station comprises a servo motor 110 driven by a servo feed back loop (126, 128) to maintain a selected speed setting 130. When an article is introduced, an impulse is applied to the article sufficient to change its state of motion from its initial state to the selected speed setting. That impulse is applied by the servo motor 110, and the system captures data indicative of the applied impulse, by monitoring the motor current (140, 142). A processor 140 or software converts the captured data to determine a weight of the article, based on stored calibration data 148.