Two tiny spheres of mass 6.80 mg carry charges of equal magnitude, 72.0 nC, but opposite sign. They are tied to the same ceiling hook by light strings of length 0.530m. When a horizontal uniform electric field E that is directed to the left is turned on, the spheres hang at rest with the angle theta between the strings equal to 50.o degrees.
(a) Which ball (the one on the right or the one on the left ) has positive charge ? What is the magnitude E of the field?