Then I brought them back to the carpet and we talked about what they noticed. We wrote our "scientific observations" on chart paper. The kinders noticed that if the track was long they had to give a bigger push. If that track was shorter they had to give a smaller push.
Then, I told them that scientists sometimes do an experiment and then something else pops up that they wonder about. I told them that while they were doing this experiment, I was wondering if the push they gave would be different on a different surface. So, we moved one piece of tape at each table to a different surface- the classroom carpet, the meeting area carpet, the library carpet and the tile floor. This time their job was to try the push on both surfaces and compare how big/small a push they needed to give the car on the different surfaces.
Wow! Lots of science going on and some fairly deep topics that they've just begun to brush the surface of, but it's a good start.
By the way, I found a great resource from TpT where some of these ideas came from. I adapted a bit, but it's a great unit (and motion units for kinder are hard to find). It's from Kindergarten Squared. Click here for a link to the product at their store.