Suppose we have a large number of identicall paricles, very small in size. Any two of them at 10cm separation repel with a force of `3xx10^(-10)N`.
(a) If one of them is at 10 cm from a group (of very small size) of n others, how strongly do you expect it to be repelled?
(b) Suppose you measure the repulsion and find it `6 xx 10^(-6)N`. How many particles were there in the group?