Page 69 Section Review 3-1,3-) When an acrobat reaches the equilibrium position, the net force acting along the direction of motion is zero. Why does the acrobat swing past the equilibrium position?

According to the 1st law of motion (the law of inertia), the acrobat past the equilibrium position because he/she is initially in motion.
(or it gains momentum as approaching to equilibrium position and pass there with that momentum)