What is FRICTION? The Force of Friction – What is It? Friction can prevent motion If an object is not moving and a force attempts to slide it across a surface, the force of friction will also act on the object. Friction between the object and the surface tries to keep the object from moving. This is one effect of friction, to stop objects from slipping. Friction can oppose motion If one object is sliding across another, the force of friction will always try to stop this slipping. The force of friction acts in the direction opposite to the direction in which the object moves. Friction will either slow down the object, or make it more difficult for other forces to keep the object moving. Friction can create motion There are certain times when friction stops slipping from taking place but actually creates motion! Friction prevents car tires from slipping. Without the friction between your car tires and the road, the tires would slip and the car would not move. That is why schools are closed when it is icy. Think about what might happen when bus tires try to move on slippery roads! This is an example of friction creating motion. When friction causes an object to move we usually call it a traction force. But remember traction is really friction. The amount of Friction depends on… Texture of the two contact surfaces What are types of surfaces? What types would cause more friction? How hard the two surfaces are pressed together What variable might contribute to how hard they are pressed together? How will friction change with increased pressure? How does FRICTION affect energy transfer? The force of friction does WORK Friction transforms KE of a moving object(s) into HE Think of a time this is a desired outcome… Friction can also transfer energy to an object Tires are designed to maximize friction in order for a car to gain KE. What factors can you think of that might influence the force of FRICTION?