Question

it is easier to to pull a roller than to push it .why?

Answer 1

When moving horizontally, friction is an issue. When you pull a heavy object towards you, your pulling tends to bring the object up off the ground, which reduces friction that in turn reduces the effort required. However, when you push a heavy object away, the object stays on the ground (you are usually pushing downwards or horizontally, and rarely upwards), maximizing friction that in turn increases the effort required.