A particle of charge Q is fixed at the origin of an xy coordinate system. At t = 0 a particle (m = 0.771 g, q = 4.15 µC is located on the x axis at x = 18.2 cm, moving with a speed of 36.7 m/s in the positive y direction. For what value of Q (in µC) will the moving particle execute circular motion? (Neglect the gravitational force on the particle.)