1. The balance spring of a watch is a hoop 1.2 cm in diameter, with a mass of 0.65 g. If the watch is running 45 seconds per day too fast, by what percentage should the rotational inertia of the hoop be changed? 2. Relevant equations: I = mR^2 Ia = -k(theta) x(t) = Xm Cos(wt + @) (just using @ for phase constant) T = 2pi ( I/mgL)^0.5 3. Rotational inertia = (0.00065 kg) x (0.006)^2 = 2.34 x 10^-8 I actually have no idea where to go from there.