A particle of charge Q is fixed at the origin of an xy coordinate system. At t = 0 a particle (m = 0.800g q = 4.00?C) is located on the x axis at x = 20.0 cm, moving with a speed of 50.0 m/s in the positive y direction. For what value of Q will the moving particle execute

A particle of charge Q is fixed at the origin of an xy coordinate system. At t = 0 a particle (m = 0.800g q = 4.00?C) is located on the x axis at x = 20.0 cm, moving with a speed of 50.0 m/s in the positive y direction. For what value of Q will the moving particle execute circular motion? (Neglect the gravitational force on the particle.)