I apologize if someone already posted a pendulum solution. Attached is a Squeak solution to the problem assuming the small angle approximation (theta is approximately sine theta) and starting the pendulum from rest. It uses the same motion ideas of position, velocity, and acceleration as the freefall problem already discussed. It uses simple Squeak blocks to approximate the solution by solving two first order differential equations numerically and displaying the result as a moving pendulum - very similar to the freefall problem. The added twist is that the acceleration depends on position (in this case an angle). It could be the next problem after freefall. I'm not sure how to teach it to young kids, but if they got the freefall problem, then ask them: "Now what if the acceleration isn't constant? Let's find out."
You can experiment to see the effect of mass, gravity, and length. There is no effect from mass - it is put in because it is a common misconception. Probably there should be an angle watcher so that starting angle could be varied, however the simple solution modeled here breaks down for large angles and that would have to be carefully explained.
Randy Caton
-- I am on leave from Christopher Newport University from Fall 2002 to Fall 2004. I will be at NASA Langley Research Center. However, I will still use rcaton@cnu.edu as my email.
Randall Caton NASA Langley Research Center Hampton, VA 23681-2199 voice: 757-864-5032 FAX: 864-8835 email: rcaton@cnu.edu web: www.pcs.cnu.edu/~rcaton
squeakland@lists.squeakfoundation.org