[SOLVED] Kinetic and Static Friction I've done so many of these but for some reason can't figure this one out. Any help iwll be greatly appreiciated. Here is the problem: A book of mass M = 0.55 kg rests on a table where the coefficient of static friction μs = 0.48. What is the minimum horizontal force needed to move it? So I draw my free body diagram and get this N=m*g P=μs*N where N is normal force, P is horizontal force P = 2.59 N This part is correct Now for the part I can't solve. A different force of F = 3 N now acts on the book at an angle of θ = 30 deg above the surface of the table. What is the acceleration of the book if the coefficient of kinetic friction μk = 0.25? I've tried this part two different ways. First I checked for movement Fy+mg = N f = μs*N Fx - f = ma Fx-μs(Fy+mg)=ma 3cos30-.48(3sin30+.55*9.81)=ma -.712 N = ma since friction force > applied force, the book doesn't move so acceleration is 0. However, they don't like that answer. So now I assumed the book must already be in motion when the force is applied which is why they give me a kinetic friction coefficient. Fx-μs(Fy+mg)=ma 3cos30-.48(3sin30+.55*9.81)=ma .874 N = ma a = 1.59 m/s^2 They don't like this answer either. Can anyone helpshed some light on what I"m doing wrong? Thanks so much in advance.