Η δύναμη της τριβής κρατά το κουτί ακίνητο Original Khan Academy video: Force of Friction Keeping the Block Stationary https://www.khanacademy.org/science/physics/forces-newtons-laws/inclined-planes-friction/v/force-of-friction-keeping-the-block-stationary Help us caption & translate this video! http://amara.org/v/CL5O/