1. The problem statement, all variables and given/known data It says: A 20kg object is placed on a horizontal surface. A force of 3N is required to keep the object moving at a constant speed. What is the coefficient of friction between the two surfaces? I figured that we know that Ff=uFn and Fn=Fg=mg therefore Fn=20*9.8=196N That's as far as i can go...i am not sure what to do with the 3N force. The answer in the books says that u is .15 2. Relevant equations Fn=Fg=mg Ff=u*Fn 3. The attempt at a solution Fn=20*9.8 =196N I'm lost from here...not sure what to do to solve for coefficient of friction given horizontal 3N force etc. Help please?