1. The problem statement, all variables and given/known data A ramp with an angle given by ø (from the horizon) and a box of mass represented by "m" with a given µ=0.55 between the ramp and the box, find the minimum (critical) ø for which the box will begin to move down the ramp. Wether µ is kinetic or static is not given in the question. 2. Relevant equations These equation are all in respect to the x and y axes being rotated such that they are lined up with the ramps surface Fg=mg Fgx=(sinø•mg) Fgy=-(cosø•mg) Fn=-(Fgy) which equals cosø•mg Ff=µFn which equals 0.55(cosø•mg) and since we label down the ramp as +, Ff=-0.55(cosø•mg) I think that is all we will need + some trig identities 3. The attempt at a solution I'm really not to sure how to set this question up. Any and all help is much appreciated. If you could label all forces acting upon the box with the same terms that I have, that would be very helpful.