My Best Topic in Physics Laboratory (Friction)

                            
             My best experiment in our laboratory was about friction. It kinda' interest me to know that friction is not just a simple kind of force affecting our daily activities but also it affects our life.Knowing everything about friction makes makes me feel to know more about it thus building up my curiosity level to be at the peak.

             Friction is defined as the opposing, resistive force between two objects that acts to hinder the relative motion between the two of them. It is always the same to the force applied on the object but it is always directed in the direction opposite to the direction of the motion.
 
             Frictional resistance to the relative motion of two solid objects is usually proportional to the force which presses the surfaces together as well as the roughness of the surface. Since it is the force perpendicular or "normal" to the surfaces which affects the frictional resistance, this force is typically called the "normal force" and designated by N. The frictional resistance force may then be written:

ffriction = μN

μ = coefficient of friction μk = coefficient of kinetic friction μs = coefficient of static friction

Standard model of friction

The frictional force is also presumed to be proportional to the coefficient of friction. However, the amount of force required to move an object starting from rest is usually greater than the force required to keep it moving at constant velocity once it is started. Therefore two coefficients of friction are sometimes quoted for a given pair of surfaces - a coefficient of static friction and a coefficient of kinetic friction. The force expression above can be called the standard model of surface friction and is dependent upon several assumptions about friction.

Friction and Surface Roughness