I was recently building an assembly with about 30 parts.  There were bearing and shafts, so some of the parts were moving.  After it was built I forgot on bit of information.  Gravity.  How do I include this into my assembly.  I had hinges in the wrong places so, some parts were moving down when I wanted them to go up.  Here is a simple fulcrum with two spheres.  Lets assume the small one weighs 50 lbs and the large one 1 lb.  How can I add gravity to show effect.  I know I can change material, but my original assembly had numerous parts and several different materials.