A student pulls a rope attached to a box of books and moves the box down the hall. The student pulls with a force of 185 N and an angle of 21.0º above the horizontal. The box has a mass of 45.0 kg and the coefficient of kinetic friction between the box and the floor is 0.27. Find the acceleration of the box. Take this problem in steps:

Find the horizontal force the student is applying on the object by using this equation: Ff= u*m*9.81 so it should look like this: 185*cos(21);
Then find the force of friction by using this equation: F horizontal - Force friction=μ×m×9.81 where \muμ is the coefficient of friction.
Then, find the net force acting on the object by subtracting the 2 forces like this:


Then, divide this answer by the mass to determine the acceleration.