Coulomb's Law regarding theta and plotting

[iberhammer]

Homework Statement

In lab, there was a string with a charged ball, and another charged ball moved closer to it. The ball's repelled and we had all sorts of data to calculate. I did a graph of the D vs 1/R^2 and the points fell almost right on. However, towards the end of that line, the points started to spread out a little more. Meanwhile at the beginning, the points looked really close to each other.

My question is why does that happen towards the smaller R values? The smaller R values are the ones near the end all dispersed? The smaller the R value implies that the balls are really close so there is an attraction to the negatively charged particles within the ball on the string and due to the weight of the ball, the ball will drop until they touch? Am I correct?

It also says that a small enough angle can deplete the need for a tangent of theta by replacing it with the sine of theta (D/L). The question says "for what range of angle theta is this a good approximation?" I'm assuming from 0 to 45 degree??

Thank you in advance for any help :)

 

[Maxim Zh]

If the balls are conductive the charges can redistribute inside them. This effect is considerable for short distances.