일반물리학 2 — Electric Potential: Problem 60

60 In Fig. 24-46, a plastic rod having a uniformly distributed charge \(Q = -28.9 \text{ pC}\) has been bent into a circular arc of radius \(R = 3.71 \text{ cm}\) and central angle \(\phi = 120^\circ\). With \(V = 0\) at infinity, what is the electric potential at \(P\), the center of curvature of the rod?