A negatively charged pith ball (mass 6.00 x 10-3, charge – 1.50nC) is suspended vertically from a light nonconducting string of length 15.5 cm. This apparatus is then placed in a horizontal uniform electric field. After being released, the pith ball comes to a stable position at an angle of to the left of the vertical.
(a) What is the direction of the external electric field?
(b) Determine the magnitude of the electric field.