Using a WinRAR or 7-Zip archive for physics assets is standard practice for several reasons:
Depending on what this file is for, "Rules of Gravity" could mean very different things:
If you’ve received or downloaded this archive, your first step is extraction. Use a reliable tool like The Unarchiver (for Mac) or WinRAR (for Windows). Once open, look for a readme.txt or manifest.json file—this will act as the "manual" for the gravity rules contained within.