A student swings a ball at the end of a string of length R in a vertical circle as shown. The ball moves with the minimum speed necessary to complete a circular path at point 1. Consider the system of the ball. In terms of the mechanical energy of the system, which of the following claims is correct, and why? The system is open, because the ball is able to complete a full revolution around the circle. B The system is open, because a net force is exerted on the ball as it travels in a circle. C The system is closed, because the ball is able to complete a full revolution around the circle. The system is closed, because the speed of the ball remains constant as it travels in the vertical circle.
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