Sledding season provides children with a wonderful, natural way to learn about sliding and friction. Next time you go sledding with your child, experiment with some different sliders and decide together which one is the fastest. Try purchased sleds, as well as homemade ones, such a piece of cardboard.
If you are indoors, try sliding different household objects down a homemade hill. Hills can be made from all kinds of things around the house, like a flat baking sheet or a blanket draped over some pillows. What things slide the fastest? What things don't slide at all? Do some things slide on one kind of hill, like the baking sheet, but not on another kind of hill, like the blanket?