What is Friction?
Friction is the resistance offered to the movement of one material against another. It could be any two materials you can think of. Many of the jobs and activities we carry on in life would be impossible without friction. Without friction, the belts of machines would slip, nails and screws wouldnt hold, feet would not grip the floor or pavement, wheels would spin without making things move! Yet in many cases, especially in machines, we actually try to reduce friction as much as possible. In the case of solid things, friction is caused mainly by unevenness in surfaces that touch each other. The smoother these surfaces, the less friction. Interestingly enough, friction between unlike materials is less than that between substances of the same kind. When we lubricate the surfaces, as when we oil the bearings of machines, we reduce friction by substituting liquid friction for solid friction. Friction between solids is of two kindssliding and rolling.
• Friction is a force between two surfaces that are sliding, or trying to slide across one another, for example when you try to push a toy car along the floor. • Friction always works in the direction opposite from the direction the object is moving, or trying to move. It always slows a moving object down. • The amount of friction depends on the materials from which the two surfaces are made. The rougher the surface, the more friction is produced. For example, you would have to push a book harder to get it moving on a carpet than you would on a wooden floor. This is because there is more friction between the carpet and the book than there is between the wood and the book. • Friction also produces heat. For example, if you rub your hands together quickly, they get warmer.
