1. The problem statement, all variables and given/known data I've got a few physics homework questions I need a bit of help with. All relate to friction. Here's the first one: The µs = .2 between the boxes. Mass 2 (80kg) is on an air table. What minimum force will keep mass 1 (40kg) from slipping? What is the maximum acceleration that will keep the mass from slipping? Here's a pic I drew up with FBDs. 2. Relevant equations 0.2Fn+Fsin30=mg or 0.2Fcos30+Fsin30=mg 3. The attempt at a solution If I solve for F I get 582. 289N but the answer I was given is 637N. Where did I go wrong? or is that the right answer? I think it's because I didn't account for mass 2 moving when the force is applied but I'm not sure how to do that.