1. The problem statement, all variables and given/known data This problem is regarding Friction Force: Imagine a skateboard, low and with well-oiled bearings. What would happen if, standing over it at rest, you begin to walk along its length? 3. The attempt at a solution There are 4 options. I chose this one: It would start moving in the opposite direction. The book says it's the correct Answer, but I'm not quite sure why that is. Is it because the Static friction coefficient is bigger than the force I exert on the skateboard by walking? P.D. Would it be against the rules if I post a new question, about the same topic in this same thread, once I get the last one answered?