Question

A tiny ball of mass 0.60 g is suspended from a rigid support with a piece of thread in a horizontal electric field of intensity 700 N/C. The ball is in equilibrium when the thread is inclined at an angle of
20o
to the vertical. What are the magnitude and sign of the charge on the ball? Take
g=9.8m/s2
−3.1×10−6C
3.2×10−6C
4.2×10−6C
−4.1×10−3