My alma mater, the University of Colorado, Boulder, has put together a fantastic website called PhET. It’s full of interactive simulations for all branches of science, and for math. The simulations run from the very basic for elementary school students, all the way up to university-level material.
I learned about PhET a few years ago, and have been using it with my kids as part of our homeschool studies. We studied chemistry last year, and the kids got to play with atoms, acids and bases, density, and the pH scale. We will study physics this year, and address motion, force, springs, waves, light, sound, magnetism, and electromagnetism.
The PhET simulations are fantastic for helping kids learn about how science works. They get to play with each of the variables in a system, and see how changing one affects the others. They can shoot a piano from a cannon, or make their own atom from scratch. They can pilot a lunar lander, or watch a glacier move. Kids are able to get silly, and try things that they wouldn’t be able to try in real life.
It’s never too early to introduce kids to complex topics. My kids are 12 and 9, but I’ve successfully introduced them to concepts that I didn’t learn about until high school or college; laying the groundwork for later study is a big part of my educational philosophy.
The PhET simulations are extremely well done, and it’s a great chance for your kids to get to design their own skate park and play with its physics. I recommend the entire site to any science- or math-oriented kids and adults. The simulations are all available for free.