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.
Lots of girls experience cramps before or during their periods. Cramps are caused by prostaglandins (say: pross-tuh-GLAN-dinz), chemicals a girl's body produces to make the muscles of the uterus contract. The contracting muscles help push the blood out through a girl's vagina during her period. You probably know periods usually come once a month. Sometimes, younger girls aren't that regular, so they may skip a month. But as a girl's periods get more regular, cramps are more likely.