Question: In the rotating disk and strobe demo. we observed that different flashing rates of the strobe light would make the spot on the disk stand still or move in different directions.
(a) Assume that the disk is rotating clockwise at a constant speed of 13 rev/sec. If the flashing rate is 15 times per second, express the movement of the spot on the disk as a complex phasor, pin that gives the position of the spot at the nth flash. Assume that the spot is at the top when n = 0 (the first flash).
(b) For the conditions in (a). determine the apparent speed (in revolutions per second) and direction of movement of the "strobed" spot.
(c) Now assume that the rotation speed of the disk is unknown. If the flashing rate is 13 times per second. and the spot on the disk moves counterclockwise by 15 degrees with each flash, determine the rotation speed of the disk (in rev/sec). If the answer is not unique, give all possible rotation speeds.