This Newton's Second Law module is a nice mix of text, videos, and simple Sims. They appear NOT to work on iPad, but they seems like they'd be pretty easy to create from a template. I think the Sims Jim Coffield created in Flash were much more sophisticated than these.

Basically, you start with reading some text. There may be a video or a sample problem that is immediately responded to with True or NO, followed by the explanation for why the response is or isn't True.

There is a simple 3-space ship race sim, each with a different acceleration - the no. of aliens can be changed to balance the net forces on the 3 space ships. Only one variable can be changed in this sim, inertia, or the number of aliens.

I would rather they call it increasing the aliens increasing the mass. It would be simple to recreate using more manipulatives, and add some F=ma calculations. About five would be adequate. Feedback could be both print and read.

You have to be a member of NSTA to use this resource. I am a member.

The National Science Teachers Association website

http://www.nsta.org

The Force and Motion SciPack online unit is for sale members for $31.99. I seemed to have access to everything. It wasn't clear what the difference between my experience and the subscriber's would be. I noticed there was online help, which I didn't try.

http://www.nsta.org/store/search.aspx?action=browse&product=scipack