1. The problem statement, all variables and given/known data A 6 kg object sits on a horizontal surface with coefficient of friction = .8. What is the minimum force (not necessarily horizontal) necessary to make the object slide? 2. Relevant equations fr = u * N where fr = the friction force u = coefficient of friction N = the normal force 3. The attempt at a solution I knew there was something more to this problem- In lecture, my prof talked about a "magic" angle theta in the positive x and positive y direction that would take the least amount of force to move an object is one was pulling on the object at said "magic" angle. Since no value was mentioned, I assume the angle varies with the mass and the force being applied to the object. As usual for me, I have an apparently sound free body diagram, apparently sound equations, and too many unknowns. I have normal force N, force of gravity mg, friction force fr, and the force on the object F. Fnet,x = F cos theta - fr = ma (my prof doesn't believe in the difference between Fk and Fs (static and kinetic friction) so when a = 0 is when the minimum force is being exerted to make the block move) Fnet,x = F cos theta = fr Fnet,y = N - mg + F sin theta = ma acceleration is zero in the y direction so: F sin theta = mg - N I can sub in u * N for fr and set tan theta equal to (mg - N) / (u * N), but I don't know N or theta and I'm trying to get to F. Am I approaching these problems wrong or do I just keep getting lost along the way? I feel like I keep getting stuck in the same places.