Ok, for the circular motion, where we are suppose to have 0 acceleration, this is the problem i have My question ask for mass of the washers and paper clips by equating Fc to Fg, and I am given the # of washers, The radius and the mass of the stopper. and the period now it ask me for mass how do i find this? i kno that Fc = mv^2/r or Fc = 4pi^2rm/T^2 and Fg = mg, but how do i do it? i can't seem to figure it out, even after i figure out the speed, it doesn't help, i have 2 unknowns...The Fc, and the mass... help please? Incase this helps, i am swinging the tubber sopper, with a tube, and below the tube is the paper clip to keep my distance so i kno i am swinging at a constant speed, then at the end of string is my washers for the mass.