The last part of this problem has been bothering me. I don't understand how the work done by friction can be found if you are not given the coefficient of friction. Can anyone help me with this? There is a picture attached. 1. The problem statement, all variables and given/known data Sally applies a horizontal force of 567N with a rope to drag a wooden crate across a floor with a constant speed. The rope tied to the crate is pulled at an angle of 48 degrees relative to the floor. The acceleration of Gravity is 9.8 m/s^2. How much force is exerted by the rope on the crate in Newtons? What work is done by Sally if the crate is moved 34.1m? Answer in units of Joules. What work is done by the floor through force of friction between the floor and the crate? Answer in units of Joules. 2. Relevant equations 567cos(theta) = F W = F*d 3. The attempt at a solution So far I've found the answer to the first and second question. Force of rope = 567/cos(48) = 847.3682038 N Work done by Sally = 567*34.1 = 19334.7 J I don't think that this last part can be done without the coefficient of friction. Am I wrong?