More physics, please help me ... (Preparation for an exam.)?

This topic is enormously hard for me and in the main text book which I use, all the provided material is introduced literally in the most difficult way. :((( May somebody help me to figure out... 3. In the exam I will probably me asked to the explain the diagrams and graphics, so I have found this task the point... show more This topic is enormously hard for me and in the main text book which I use, all the provided material is introduced literally in the most difficult way. :(((
May somebody help me to figure out...


3. In the exam I will probably me asked to the explain the diagrams and graphics, so I have found this task the point of which is to show the direction of the electric field at the point A and then at the point B but how can I find out that if there is no information if the particle (A or B) is positively charged or negatively….

 (pic)

4. Lets assume that the Earth and the Moon have received the same charge (+q), How large should the charge be so that the gravitational force between the Earth and the Moon is equivalent to the “electric removal force”?


This task I don’t understand at all. I have tried to count everything by different formulas and by using the masses which the google gave me but the results are very weird and cannot be right for sure. But I guess it is quit the same as the second question in theoretical part and I did not understand it, in the first place..... as I have mentioned before. T…T
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