r A thin glass rod is bent into a semicircle of radius r. A charge +Q is uniformly distributed along the upper half, and a charge -Q is uniformly distributed along the lower half, as shown in the figure. Find: 1) The direction of the electric field at the center O of the semicircle as a function of Q and r. [1 marks] 2) The magnitude of the electric field at the center O of the semicircle as a function of Q and r. (hint: which component cancels out, x or y?) [2 marks] 3) The force felt by a charge qo=2.0 x 10-7 C if this charge is placed at point O. [1 marks]