Friction and the Real Area of Contact

Friction and surface texture - If I need to move a heavy block, it seems like it should be easier if I stand the block up rather than laying it flat on its face...and yet, as Leonardo Da Vinci observed, the size of the contact area doesn't seem to affect friction. The reason why lies in the difference between the Real Area of Contact and the Apparent Area of Contact. In this video we zoom in on surface roughness to understand what's really happening when rigid surfaces come into contact...and how surprising little "contact" can actually support a load.