Describe some examples where we deliberately increase friction. 

We deliberately increase friction by using brake pads in the brake system of bicycles and automobiles. When we are riding a bicycle, the brake pads do not touch the wheels. But when we press the brake lever, these pads arrest the motion of the rim due to friction. The wheel stops moving. Kabaddi players rub their hands with the soil for an easy grab of their opponents. Gymnasts apply some coarse substance on their hands to increase friction for better grip.