When can you assume that gravity is the only "applied force" opposing friction? 1. The problem statement, all variables and given/known data "Determine the stopping distance for a skier moving down a slope with friction with an initial speed of 24.7 m/s. The slope makes an angle of 5.02deg above the horizontal, and assume that μk=0.172." For this question, I have three variables that I don't have values for -- normal, mass, and acceleration. Since I only have two equations (sum of the forces for F(x) and F(y) directions), I can only have two unknowns for me to solve the problem. Am I supposed to assume that the acceleration is 9.8m/s/s (acceleration due to gravity) in this case? 2. Relevant equations Fnet = ma 3. The attempt at a solution Fnet(x) = n - W(x) = ma --> n - Wcos(theta) = ma Fnet(y) = f(k) - W(y) = 0 --> f(k) - Wsin(theta) = 0 With my method of assuming that a=9.8m/s/s, I then isolated for "m" in each equation. (1) m = n / [a +gcos(theta)] (2) m = μ*n / [gsin(theta)] I then equated both formulas to each other, to solve for the normal, "n".