1. The problem statement, all variables and given/known data A student pulled a box of books weighing 68kg by a rope at an angle of 58 degrees above the horizontal plane of the floor. The floor has a coefficient of kinetic friction of µk=.27. What is the acceleration of the box of books? 2. Relevant equations ∑F = ma Force of friction = µk * Normal force 3. The attempt at a solution I chose the direction the box of books was being pulled to be positive. Then I summed up all the forces in the x direction and applied Newton's Law F=ma and solved for a. ∑Fx = Force from rope in the x direction - Force of friction = ma ∑Fx = 68*cos(58) - .27*(68 * 9.81) = (68)a solve for a. This problem was on my final yesterday so the numbers arent correct but is my reasoning and approach to this problem right? I thought i knew how to do these types of problems but the answer i was getting wasnt a choice on the test. Thanks in advance.