I'm not really sure about how to go about this problem. It says: After every full moon, Mr. Sowell likes to slide around the hallways on freshly waxed floors in his socks. If the U* between the socks and the floor is 0.120 and amount of force required to move him 102 N, what was his mass in kg. If i just knew which formula to use, and what each thing stood for i'm pretty sure i'd be able to solve this. the U* that i wrote is the funny looking greek U calle mue or whatever. Please help me someone!!!