Ana is redecorating her apartment. She slowly pushes on 80kg china cabinet across the wooden dining room floor which resist the motion with a 300N force of friction. What is the coefficient of sliding friction between the china cabinet and the floor?

Friction force is the coefficient of friction \mu times the normal force. For an object sitting on a level floor the normal force is its weight:


F_f = \mu mg


You have everything you need to solve for \mu

Ff=mass*gravity*coefficient of kinetic friction. So 300=80*9.81*coefficient. Shoulud be.3823

If 6 Joules of work are done on a 6kg box that is moved 3 meters, how much force is applied to the box?
W= Fd:
D=?
F=?
W?

You are told that 6 joules of work are done so W=6 joules. It is moved 3 meters, so d = 3 meters. Now you can calculate the force, F, using W=Fd.