A marble moves along the x-axis. The potential-energy function is shown in Fig. (a) At which of

Question:

A marble moves along the x-axis. The potential-energy function is shown in Fig.
(a) At which of the labeled x-coordinates is the force on the marble zero?
(b) Which of the labeled x-coordinates is a position of stable equilibrium?
(c) Which of the labeled x-coordinates is a position of unstable equilibrium?

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