A mass m is at the end of light (massless) rod of length R, the other end of which has a frictionless pivot. The rod is initially horizontal and the mass is pushed down with an initial speed vo.
What is the change in potential energy of the mass, when it goes from this starting position to the top of the circle ("12 oclock")
PINK: mgR
BLUE: 2 mgR
YELLOW: 3 mgR
GREEN: - mgR
PURPLE: something entirely different
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