Lab 106(2): Static and Kinetic EquilibriumPhysics 111A 029October 20, 2017Partners:Instructor: IntroductionWhen a surface of one body slides over another surface, each body exerts a frictional force on each other that is parallel to the surfaces. Additionally, the direction of friction is opposite to that of the motion of the sliding body. For a body at rest, it exerts a downward gravitational force onto the surface on which it lies, that responds with a normal force perpendicular to the surface. When a force is applied to that body, along the x-coordinate, there is an initial frictional force that responds to that force, that resists the movement of the object. This frictional force is called static frictional force. When the force applied is enough to cause the body to slide it can be said that the applied force is greater than the maximum static frictional force. The force that acts on the body in movement, would then be called the kinetic frictional force. The kinetic frictional force is less than the maximum static force, which means that there is no needfor any additional applied force to keep the body in motion. The relationship between the maximum frictional force and the normal force is called the coefficient of static friction.fs,max=sFNwhere sis the coefficient of static friction,fs,maxis the maximum static frictional force and FNis the normal force . The kinetic friction force can be calculated using the following formula:fk=kFNWhere fkis the kinetic frictional force and kis the coefficient of kinetic friction. If the sliding occurs at a constant speed, Newton’s First Law of Motion (body at rest stays at rest vs a body in motion stays in motion) can be applied to the system. Static and kinetic coefficients depend on the interaction of the two surfaces in contact with each other and are each independent of the normal force exerted between the two surfaces. On a frictional force vs. normal force the slope of the line will be the coefficient of that frictional force.