• Types of Friction

    Generally, there are following types of friction.

    Static Friction

    The force of friction which comes into play between two bodies before one body actually starts moving over the other is called static friction (fs). Static friction prevents the sliding of two surfaces relative to one another. In this case, the object remains at rest because the static friction is equal in magnitude and opposite in direction to the applied force. As the applied force on the body is increased, the static friction is also increases. Thus, this frictional force is a self adjusting force.

    The magnitude fs of the static frictional force can have any value from zero up to a maximum value of fsmax, depending on the applied force. In other words,                                                                

               fs < fsmax = μsFN

    Where μs is the coefficient of static friction and N is the magnitude of the normal force (the force perpendicular to the surface).

    A maximum amount of static friction (fsmax) must be overcome to cause a stationary object to begin to move. The maximum force of static friction which comes into play when a body just starts moving over the surface of another body is called limiting friction.