In some cases, we deliberately increase friction. Explain why?
We need to increase friction in some cases like grooving in the sole of shoes, the treaded tyres of cars, trucks or other vehicles, using brake pads in the brake system of bicycles and automobiles. If we do not do so, we may slip on the floor or roads, vehicles may slip on the roads and they will not stop, our bicycles and automobiles will not stop, etc.