1. Friction: This is a force that opposes motion between two surfaces in contact. It can be caused by the roughness of the surfaces, the pressure between them, and the type of material involved. Friction slows down objects by converting their kinetic energy (energy of motion) into heat. Examples include rubbing your hands together, a car braking, and a ball rolling across the floor.

2. Air Resistance (Drag): This is a force that opposes the motion of an object through the air. The amount of air resistance depends on the object's shape, size, and speed. Air resistance acts to slow down objects by creating a force opposite to their direction of motion. Examples include a parachute slowing a skydiver, a car traveling at high speeds, and a ball falling through the air.