Question

A positively-charged piece of plastic exerts an attractive force on an electrically neutral piece of paper.

Why is this because of " the electric force between charged particles decreases with increasing distance."

what does that have to do with this?

Answer 1

When the positively charged piece of plastic is brought near the initially neutral piece of paper a negative charge is induced in the paper. For this to happen the paper must be capable of conduction. Normally there is moisture content in paper that assists conduction. The opposite charges on the piece of plastic and piece of paper give rise to a force of attraction that is inversely proportional to the square of the distance between the pieces.

Answer 2

then shouldn't it be something like "electric force between charged particles increases with decreasing distance"

Answer 3

Although stricctly both statements are correct, I agree that "force increases with decreasing distance beteen the charges" is easier to visualise.