I had so much fun updating the Top 10 FREE Apps for Life Science post (now 18 free!) that I had to do the same for the Physical Science list.
There are now 15 great apps on the Physical Science list, plus a bonus! NASA has an additional 31 apps for free. I didn't check them all so they're not officially counted, but several of them look amazing. Download and try them out, then let us know which deserves an official place in the list.
Check out the newly updated list!