When 7-year-old Sophia and I were playing on the swings at the park, a small boy several times crossed the path of my swing. Despite our smiling words of caution, I found myself wrenching to a stop to avoid hitting him. In order to show the boy the actual path of the swing, and the path he should follow in order to be safe, I took a moment to explain. First I backed up a little and said, "See? When I'm back here, it looks safe where you are, but let's see what happens if I swing forward -- and -- "
Just then, Sophia interrupted helpfully, shaking her head, "Mommy, he's still very little, and I don't think he'll understand about momentum -- "