She 'is' well/solidly 'grounded in' mathematics. [=she has a good basic knowledge of mathematics]
It turned out that our fears 'were' well 'grounded'. [=there was a good reason for our fears]
She discussed the principles on which her philosophy 'is grounded'. [='based, founded']
(..) No, this is wrong. They're not coming back to life--they're still dead! My decorpsinator serum--it's incomplete! Must...Eat...Sugar! You're grounded, Mister. Oh, this is really bad. They're going to be attracted to the Candy Kingdom! Why? Because the Candy People (..)2010 TvShow: Adventure Time Title: Slumber Party Panic Season: 1 Episode 1