How does friction provide an unbalanced force on a sliding object?

According to Newton’s first law of motion, an object will maintain its state of rest or uniform motion unless acted upon by an unbalanced force. When an object slides across a surface, it eventually comes to rest because friction acts as an unbalanced force that opposes the object's motion.123

Specifically, friction provides this force by acting parallel to the surface in the direction opposite to the object's velocity. Because this frictional force is not balanced by any forward force once the initial push is removed, it creates a net force on the object. According to Newton’s second law, this net force results in an acceleration—in this case, a deceleration—that causes the object to lose speed until it stops. Thus, friction serves as the external influence that compels a sliding body to change its state of motion.3412