without friction nobody would be able to move without falling. Friction depends on two things: the nature of the surface and the normal force. There is also two categories of friction: static (not sliding) and kinetic (sliding). As you can see, in this video an excited sports fan slips on ice while being featured on the news. He slips so suddenly because the friction on ice is 0.02. Clearly the friction of ice is very slim. Another cause is that he went from the friction of the pavement to the friction of the ice which proves to have a significant difference in amount of friction. As he initiated the fall, the force of gravity pulled him down to the pavement where he landed abruptly. He demonstrated kinetic friction because he was sliding.