Physics

The situation where friction is not useful is sliding a heavy box easily on a floor.

In this situation, friction is not useful because it resists the motion of the box, making it harder to slide. High friction would make it difficult to move the box.

Other situation:

Option A: Walking on the ground

Friction is essential for walking. When we walk, we push our feet backward against the ground. The frictional force between our shoes and the ground acts in the opposite direction (forward), allowing us to move forward. Without friction, our feet would slip, and we would not be able to walk properly.