1. The problem statement, all variables and given/known data A car is driving up a slope at angle 16 deg. to the horizontal, trying to accelerate as much as possible. The static and kinetic friction coefficients are .90 and .80, respectively. Find the maximum possible acceleration (assuming a sufficiently powerful engine). 2. Relevant equations Fs,max = .90 x normal force Max acceleration = -mg(sin16) + fs,max / mass 3. The attempt at a solution Ok, I've seen a problem similar to this one and (plugging in the values from this question) it was solved using this first step: Max acceleration = -mg(sin16) + fs,max / mass. My first question is, where did the (sin16) come from? I drew a free body force diagram to look like this: EDIT: Sorry, in the image, f,static should actually be f,kinetic, since the car is accelerating.