Definition of sliding friction
When an object slides on the surface of another object, the friction force between the contact surfaces that hinders their relative movement is called sliding friction. The direction of sliding friction is opposite to the direction of relative movement. The magnitude of sliding friction is related to the roughness of the contact surface and the pressure. The greater the pressure, the rougher the contact surface of the object, and the greater the sliding friction generated. For example, the sliding friction generated by the two when using a blackboard eraser to wipe the blackboard.