Find an expression for the electric field

Question: Charge Q is uniformly distributed along a thin, flexible rod of length L. The rod is then bent into the semicircle shown in the figure (Figure 1) .

Part A: Find an expression for the electric field Eâƒ- at the center of the semicircle.

Hint: A small piece of arc length Î"s spans a small angle Î"θ=Î"s /R, where R is the radius.

Express your answer in terms of the variables Q, L, unit vectors i^, j^, and appropriate constants.

Part B: Evaluate the field strength if L = 19 cm and Q = 35 nC . Express your answer with the appropriate units.