Everything we know about science is temporary. Can we imagine that when the acrylic board was rubbed with silk, the generated electromagnetic field can drive the 14 W fluorescent tube lamps and the emerged electromagnetic attraction can draw the scissors and wood block swill around? When a wood box slides on a table, where the box slides, where the LEDs stocked right at the position of the sliding wood box under the table will be lit. Although numerous studies of sliding friction have been made and some empirical laws have been formulated, we have as yet, no clear understanding of the mechanism of friction. The effect of triboelectricity on the frictional force has not been studied and the nature of friction has not yet been finalized. In this paper, sliding friction was studied to investigate the nature of friction. We have found that the electromagnetic field will be generated when sliding happens, which leads to the generation of electromagnetic attraction. The generated electromagnetic attraction will accordingly affect the force of friction between two objects. Thus, we deduced that friction force should originate from the synergistic effects of the external resistance arising from uneven surfaces and the generated electromagnetic attraction. A slightly supplement and modification to the numerical formulas for calculating the sliding friction force is attempted to present. This study tries to unify the engagement theory and the adhesion theory and understand the nature of friction better. What's more, it will provide a novel perspective and open a new line of thinking for classical mechanics.