Question

A charge of 16.0 nC is uniformly distributed along a thin, flexible rod of length 31.0 cm. The rod is then bent into a semicircle, evaluate the electric field strength from the centre

Answer 1

nobody knows

Answer 2

r = .31/pi
I'm going to go out a limb and say side to side effects cancel and we cab treat it a s a point charge at the center of the semi-circle.
E = kQ/r^2 (from above)