Question

5. (a) Find the electrostatic potential at the point P in the figure below. (b) Suppose the three charges shown below are held in place. A fourth charge, with a charge of +6.11 µC and a mass of 4.71 g is released from rest at point P. What is the speed of the fourth charge when it has moved infinitely far away from the other 3 charges   

Answer 1

a)

Net electric potential at P is given as

V_p = V_a + V_b + V_c = (k Q_a / AP) + (k Q_b / BP) + (k Q_c /CP)

V_p = (9 x 10⁹) [(7.45 x10^-6) /(1.0825) + (2.75 x10^-6) /(0.625) - (1.72 x10^-6) /(0.625) ]

V_p = 7.68 x 10⁴ volts

b)

Q = charge placed at P = 6.11 x 10^-6 C

using conservation of energy

electric potential energy = Kinetic energy

Q V_p = (0.5) m v²

(6.11 x 10^-6 ) (7.68 x 10⁴ ) = (0.5) (4.71 x 10^-3) v²

v = 14.12 m/s