The children encountered a problem, however. They had difficulty knocking down the first block. Instead of experimenting with ramp height as the children in the photo did, my children experimented with different kinds of balls.
In this photo the yellow Nerf ball just bounced off the block:
The cork ball didn't work either:
Eventually they discovered a heavy metal ball (the jingly kind you roll around in your hand to relax) that did the job.
Alas, I did not record their words as they were moving fast and I was tyring to catch up with my camera. Oh, the trouble with documentation!