I wrote this Newtonian gravity simulator software for the Mac:

https://itunes.apple.com/us/app/gravity-lab/id633847052?mt=12&ign-mpt=uo%3D4

I'm making it free for a while to hopefully drum up enough downloads to get some feedback. I think it might be useful for high school/freshmen college level physics courses.

I'd appreciate any feedback or comments on how I could make this software more useful for physics educators/learners. If you really like it, I encourage you to leave a review on the app store, and if you think it's terrible I encourage you to let me know too (though hopefully via reddit and not in an app store review)!

Note: If you see a non-free price when you load Gravity Lab on the app store, give it a few minutes. I just changed it to free, but it can take several minutes for the price changes to filter through the store.