Stu

I got question 3 and 4 aha, only 12 more to go. Only 4 is below. 

Did you determine the final charge on each sphere in each case? How much charge must be transferred to achieve this final value?     (a) Rank the pairs according to the magnitude of the charge transferred during touching, greatest first.   3 > 1 > 2   1 = 2 = 3   2 > 1 > 3     SHOW HINT SHOW ANSWER

Did you determine the final charge on each sphere in each case?     (b) Rank the pairs according to the charge left on the positively charged sphere, greatest first.   3 > 1 > 2   2 > 1 > 3   1 = 2 = 3

I think just the key stuff. I missed some lectures. I found the logic analysis of these questions difficult.

Two protons (p₁ and p₂) and an electron (e) lie on a straight line, as shown. The directions of the force of p₁on e, the force of p₂ on e, and the total force on e, respectively, are:

.
And also,

The diagram shows a pair of highly charged plastic cubes that attract each other. 

Cube 3 is a conductor and is uncharged. Which of the following illustrates the forces between cubes1 and 3 and between cubes 2 and 3?

.

They have been answered now but I guess with out calculating stuff (not that i'm sure I know where to begin) but would try. However, interpreting why they will move in such a way is what I'm not clear on. Just memorising it is not enough. Mostly I was after the key principles to help with my logic. Thanks. (btw I do get most of the basics but there's gaps.)

Thanks. That and kahn acadamy helped a bit. It is integration always to get a function right? 

Melody the reason to integrate is 2 fold as far as i saw on kahn acadamy. First we want an equation of a function as a rezult zo have to undo the differentiation that has occured. Sec9ndly to apply integration is applying small change in dp and dt resprctively as inthe above example and alans explaination. Thanks guys.

Going through Kahn acadamy vids now. 

I think no xy muliplied is seperable? Is that true and the only rule?

Thanks. Doesnt n+1 happen in taking the ontgration in the later part of your reply Alan?

Great. Will have a look on the transport home for this. Seems ok. Didnt know that would be the way to solve for d though. 

I don't know so you'l probably have to watch this instead. http://m.youtube.com/watch?v=yQ6utTt1TcE 

The name of the app is listed in the post. Scientific calculator by scalea software for android.