Making Something Stop

The idea this lesson is working on — This is the chapter’s big wrong idea: that moving things run out of go and stop by themselves. Something always stops them — a hand, a wall, or the floor rubbing (friction). The same car goes much further on a smooth floor, which only makes sense if the floor was doing the stopping.

A fair test — Sam changes one thing, the floor, and keeps the car and the push the same. That is the start of a fair test, and it is worth naming whenever your child compares two things.