If a 20-kg box is slowing down as it slides right, and is experiencing a 100 N friction force; a.) what is the coefficient of kinetic friction between the box and the floor? b.) What is the work done by friction on the box as it slides to a rest in 3 meters. c.) How fast was the box moving initially? I am completely lost on part a. The kinetic energy equation is KE = 1/2mv^2, however, I cannot find a way to derive the velocity from the information I am given. Part b is easier. For that I got W = 100 N * 3 M = 300 J. I have the feeling that I could tackle part c if I understood how to do part a. Any thoughts?