According How Stuff Works, friction is good because it prevents sliding while walking, it protects vehicles from skidding by slowing them down, and it makes writing possible. Friction occurs when two surfaces come into contact. Excess friction hinders movement, and it wastes energy. Friction refers to a force that opposes motion. It is important because it is applied in almost all life processes.
How Stuff Works explains that kinetic friction occurs between moving bodies, while static friction occurs when a force on an object does not cause movement. Electrical attraction can also cause friction. The amount of friction depends on the roughness of a surface, weight of objects and opposing forces. The thickness or thinness of liquids determines the amount of friction they cause. How Stuff Works notes that friction is important in sports, such as curling and tenpin bowling. Air resistance is a type of friction that makes cycling and running sports possible.
Friction holds screws and nails in wood making structures to stand. It is impossible to eliminate all friction but it can be reduced by lubricating or smoothing surfaces. More force is needed to start moving an object against a surface than maintaining the movement. Coefficient of friction refers to the friction on a body compared to the force it imparts on a surface. Engineers calculate the coefficient of friction in order to design efficient machines.