Answer all plz

Dear Student Friction is harmful in the following ways: 1. It wastes a lot of energy, decreases efficiency of vehicles. 2. It generates heat and destroy machines. 3. It leads to rashes to your skin when we fall. 4. All forms of motion in contact with other bodies needs a constant force and thus work is done at every step. I have answered your first question. Kindly ask other questions in a separate thread. Thanks and regards