1. The problem statement, all variables and given/known data I am student teaching a class about static friction soon. I am worried a student is going to ask me where Fstatic friction = μ sFnormal comes from. I am not sure how to explain it. 2. Relevant equations 3. The attempt at a solution I've always thought of it this way. Consider a rock on a table. Normal force is a measure of how hard the table pushes up on the rock. If the normal force pushes harder, the rough surface irregularities on the table "catch" more on the rock and that increases friction. But it just occurred to me that I have NO clue if this is true. Can anyone help me out?