일반물리학 2 — Electric Potential: Problem 25

25 A particle of charge \(+7.5\ \mu\text{C}\) is released from rest at the point \(x = 60\ \text{cm}\) on an \(x\) axis. The particle begins to move due to the presence of a charge \(Q\) that remains fixed at the origin. What is the kinetic energy of the particle at the instant it has moved \(50\ \text{cm}\) if (a) \(Q = +20\ \mu\text{C}\) and (b) \(Q = -20\ \mu\text{C}\)?