Friction: Crash Course Physics #6

Why is it hard to move a heavy bookcase across a carpeted floor? And why is it easier to keep it moving than it was to get it started moving? You might think it's all about weight, but actually it's about friction. Two kinds of friction! In today's episode of Crash Course Physics, Shini Somara tells us about Static and Kinetic friction; how they work and how they're different.