So, we went to Bull Creek Park the other day, to get out of the heat, and into the creek, for a little cooling off.
After a little while, I noticed Steven was skipping rocks. I told the boys to go learn from him. Jack was super interested.
After a few tries, Steven leaned down to give Jack some pointers. He was showing him how to throw the rocks, so they’d skip.
After a few more tries, Steven leaned down to show Jack how to pick which rocks to skip:
“See this rock? This rock is good and flat, but it’s not perfectly flat. This side bulges out a little, and this other side is caved in a little. See this side? It’s convex. And this side is concave. We want to throw it with this side down. Got that, Jack?”
And Jack looked up at Steven with these “I completely understand you, but I have no idea what you said” look in his eyes. He then proceeded to throw the rock, and it skipped a little.
That is how Jack learned the difference between convex and concave. Now to get him into a 10th grade geometry class, so he retains it.