Electric field direction and force in Giancoli textbook figure

[Frankenstein19]

I'm studying for my physics exam and there is a figure on the book physics for scientists and engineers 4th edition by giancoli that i just don't understand. I know that the electric field of a negative charge points toward it and the electric field of a positive charge points away from it

Also why is the force included in that diagram, what does it mean if it is parallel to the electric field or points against it?

thank you in advanced

 

[gneill]

Please remember to use the formatting template for all homework questions.

I'm studying for my physics exam and there is a figure on the book physics for scientists and engineers 4th edition by giancoli that i just don't understand. I know that the electric field of a negative charge points toward it and the electric field of a positive charge points away from it

What is it you don't understand about the figure? What is included in parts (b) and (c) that does not appear in part (a)?

What relevant equation tells you the force that a charge experiences when subjected to an electric field?