The general solutions for the harmonic oscillator differential equation fall into four general categories: 1) Undamped: [math]x(t) = Ae^{i\omega t}[/math] This is a free-running sinusoidal oscillation that doesn't change over time.
Key Facts. 1  Itâs normal to have mild cramps during your period. 2  Menstrual cramps often start 1-2 days after your period begins. 3  If your cramps donât get better with over-the-counter medicine, you should see your health care provider.
Cramps. Lots of girls notice body or mood changes around the time of their periods. Menstrual cramps are pretty common. More than half of all women who get periods say they have cramps during the first few days. Doctors think that cramps are caused by a chemical called prostaglandin that causes the muscles of the uterus to contract.