Find direction of rotation

Imagine a disk spinning like a record player turn table. Half of the disk is black and the other is white. Assume you have an unlimited number of color sensors. How many sensors would you have to place around the disk to determine the direction the disk is spinning? Where would they be placed?

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1 comment:

Madan Kumar said...

Place 2 different sensors next to each other. You can easily see which direction it is going .