1. The problem statement, all variables and given/known data A 38.0 kg wheel, essentially a thin hoop with radius 1.13 m, is rotating at 280 rev/min. It must be brought to a stop in 15.0 s. (a) How much work must be done to stop it? 2. Relevant equations change in KE = (1/2)Iwi^2 - (1/2)Iwf^2 I = (1/2)mr^2 3. The attempt at a solution (1/2)[(1/2)(38)(1.13)^2](28pi/3) = 355.686 kg(m)^2/s I don't see where the time comes into play though..can anyone help?