Kinetic Friction

Consider a truck trying to move a stationary car. As the truck tries to pull the car, static friction is created at the contact surface.

When the applied force exceeds the limiting static frictional force, the frictional force at the interface decreases to a lesser value, called the kinetic frictional force. The car then begins to slide with increasing speed.

The magnitude of kinetic frictional force is proportional to the normal force, with the proportionality constant being the coefficient of kinetic friction.

The continued breakdown of the interface is responsible for creating kinetic friction, which resists the car's motion.

As the car's velocity increases, initially, the kinetic friction decreases slowly. However, at higher velocities, it shows a significant decrease.

The angle between the kinetic friction force and the resultant normal force is the angle of kinetic friction. It is always less than or equal to the maximum static friction angle.

The coefficient of kinetic friction depends on the surface's condition and the relative velocity between the two surfaces.