1. The problem statement, all variables and given/known data Two packages at UPS start sliding down the 20° ramp shown in Figure P8.25. Package A has a mass of 5.0 kg and a *coefficient of friction of 0.20. Package B has a mass of 10 kg and a coefficient of friction of 0.15. How long does it take package A to reach the bottom? I call the larger mass m2 and the smaller mass m1. http://img166.imageshack.us/img166/1899/p825.gif [Broken] 2. Relevant equations F=ma fk=μkn 3. The attempt at a solution I have drawn two free body diagrams. m1 up: n1 down:m1gCos(θ) left:F2 on 1 , m1gSin(θ) right: fk1 m2 up: n2 down: m2gCos(θ) left: m2gSin(θ) right:F1 on 2 , fk2 From this I wrote. Σ μ θ ΣFx1=fk1-F2 on 1-m1gSin(θ) = m1ax1 ΣFy1=n1-m1gCos(θ) therefore n1=m1gCos(θ) ΣFx2=F1 on 2+fk2-m2gSin(θ)=m2ax2 ΣFy2=n2-m2gCos(θ) therefore n2=m2gCos(θ) Now where to go from here? I am not sure but I believe I need to find the acceleration of the system since both are bound together by this law. By finding that I would then know ax1 and ax2. I'm just not sure how... two different μk confuse me, how can I find the total acceleration of the system if both are dragged by different coefficients?