[tex]This\ spring\ stretches\ in\ proportion\ to\ weight,\ that\ is,\ for\ every \\ 10\ grams\ of\ weight\ the\ amount\ of\ stretch\ is\ 5\ cm.\\ \\x\ [g]\ \ \ |\ \ 10\ \ |\ \ 20\ \ |\ \ 30\ \ |\ \ 40\ \ |...|\ \ \ a\ \ \ |\\------------------\\y\ [cm]\ |\ \ 5\ \ \ |\ \ 10\ \ |\ \ 15\ \ |\ \ 20\ \ |...|\ \ \frac{1}{2} a\ \ |\\\\a\ variation\ equation\ is\ y= \frac{1}{2} x[/tex]