A 2.00-C charged 1.00-g cork ball is suspended vertically on a 0.500-m-long light string in the presence

A 2.00-μC charged 1.00-g cork ball is suspended vertically on a 0.500-m-long light string in the presence of a uniform downward-directed electric field of magnitude E = 1.00 × 105 N/C. If the ball is displaced slightly from the vertical, it oscillates like a simple pendulum.
(a) Determine the period of the ball’s oscillation.
(b) Should gravity be included in the calculation for part (a)? Explain.