This problem deals with finding the coefficient of friction between an object and a slope. It gives an object with mass m, sliding down a hill with a slope of θ at a constant velocity. I got mgsinθ=fksinθ.

However the book shows mgsinθ=fk. The kinetic friction force and the force down the slope are parallel but directed in opposite directions, so where is my error? I included a drawing for reference.

However the book shows mgsinθ=fk. The kinetic friction force and the force down the slope are parallel but directed in opposite directions, so where is my error? I included a drawing for reference.

http://ift.tt/1xyE7Yk