Question

If we fold the paper into two halves and press it hard then it creates a line between it and then if we try to tear it apart it is much easier . Why?

Answer 1

When you fold a piece of paper hard enough there is a permanent elongation along the line of fold. So now this region has a lesser yield point ( i.e. can take lesser amount of stress). It thus forms the line of least resistance and the paper is torn along that line.