Summary Friction opposes sliding and depends on the roughness of surfaces in contact. This proportion is called the ‘Coefficient of Friction’ and is denoted by the symbol μ (pronounced ‘mew’). Friction which opposes movement from rest is called ‘Static Friction’. As soon as sliding takes place it is found that less force is required and is called ‘Kinetic Friction’. Friction is mainly depended on the nature of the surfaces and not the area of contact between the surfaces. The experiment was carried out to determine how kinetic and static friction varies and how the coefficient of friction varies with increased load or pressure on a surface and the type of material used. Wooden, metallic and rubber surfaces were used. It was found that the area of surface contacts and the amount of normal force applied to the surfaces does not influence the friction; rather, the nature of surfaces used for friction was the main contributor to the value of coefficient of friction. Experimental Objective The objectives of this experiment is to verify the laws of friction, the different types of friction (static and kinetic friction) and how the type and nature of surface on which friction takes place determines the coefficient of friction. In particular, three surfaces are investigated. These are metal on metal, wood on wood and metal on rubber. Theoretical Background Smooth surfaces are normally characterized by the nature in which they lie perpendicular to their tangent plane when they come in contact. Nevertheless, no surface however smooth it is lacks friction (CodeCogs Engineering, 2009). Friction can be defined as the resistance to sliding when two or more surfaces are in contact with each other. The frictional force is the force that inhibits the relative motion between the surfaces. Uneven particles between the surfaces are the main cause of friction. Therefore, in order for sliding to occur, this force has to be overcome. Different laws of friction exist. These are:  1. The magnitude of the friction between surfaces does not depend on the contact area.  2. The coefficient of friction (μ) depended on the composition or nature of the surfaces (the materials the surfaces are made of) tends to limit the friction when a normal force is applied.  3. The direction of friction is always opposite to the direction of motion or the direction in which sliding occurs and does not depend on the velocity of the bodies.  4. The frictional force is normally adequate in preventing friction for bodies in equilibrium and thus can easily be calculated through the application of conditions of equilibrium (CodeCogs Engineering, 2009). Static friction is defined as the friction that inhibits motion of surfaces from rest while kinetic friction occurs for surfaces already in motion. The coefficient of static friction is normally greater than the coefficient of kinetic friction. Friction has both its positive and negative aspects. In particular, friction is very essential in the braking system of vehicles. However, it causes wear and tear in machines making them consume more power. Experimental Procedures Equipment used: Sliding friction equipment, friction surface plate and block with cord, knurled