Think about what happens when a corner hits the circle. The rectangle immediately begins moving in a straight line ... until the next corner hits the circle. No straight lines in a circle, there is no purely circular motion for the rectangle or any point in it.
Think about what happens when a corner hits the circle. The rectangle immediately begins moving in a straight line ... until the next corner hits the circle. No straight lines in a circle, there is no purely circular motion for the rectangle or any point in it.