1. The problem statement, all variables and given/known data A man of 72.0kg is pushing a heavy box along a flat floor. The coefficient of sliding friction between the floor and the box is 0.20, and the coefficient of static friction between the man's shoes and the floor is 0.65N. a) If the man pushes downward on the box at an angle of 30 degrees, what is the maximum mass of the box be can move? b) If the man pushes upward on the box at an angle of 30 degrees, what is the maximum mass of the box he can move? 2. Relevant equations fk= ukN 3. The attempt at a solution So, according to the free body diagram for the man: Fx man= -ukmmang-Pcos(60) For the box: Fx box= Pcos(30)-ukmboxg I don't know where to go from here. If I set the equations equal to one another I have two unknowns (P and mbox). If I add the equations, I get the same problem, plus acceleration thrown in there. If anyone can steer me in the right direction, that would be great!