Three types of friction are distinguished: sliding friction, rest friction and rolling friction. The force of rest friction prevents solids from moving, it is always equal in magnitude to the external force acting on the body, and is directed in the opposite direction. The sliding friction force is the force that arises between the contacting bodies during their relative motion. The rolling friction force is the friction force that occurs when one body rolls on the surface of another body.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.