1. The problem statement, all variables and given/known data An object of unknown mass M is hung from a vertical spring of unknown spring constant k, and the object is observed to be at rest when the spring has extended by 14cm. The object is then given a slight push and executes SHM. Determine the period of this oscillation. 2. Relevant equations T = 1/f w = (k/M)^(1/2) = 2pi*f F=kx 3. The attempt at a solution The object is hanging, so it has a force of Mg pulling it down and kx pulling it up. It's in equilibrium at a displacement of 14cm (0.14m). So I set kx = Mg and solved for k: k = Mg / x I then plugged this into w = (k/M)^(1/2) so the M's cancel and I'm left with w = (g/x)^(1/2) = (9.8 / 0.14)^(1/2) = 70rad/s w = 2pi*f => f = w/(2pi) = 11.14 Hz T = 1/f = 0.089s This isn't the right answer according to the book, and I keep getting this kind of problem wrong. I'm not entirely sure what I'm doing wrong.