That's an awful wheelchair ramp. That shouldn't be legal!
On your own, write down rules for wheelchair ramp builders to make sure that the ramps are safe.
If kids are stuck, show them a steep ramp, and ask them to explain what's wrong with it. Push them to generalize: Can you draw a few ramps that aren't allowed? A few ramps that are?
Make the most dangerous ramp that you can while still following your partner's rule. Be cruel here: try to break the spirit of the law while still meeting its requirements.
After a few minutes, we pool all of the kids' rules together.
My favorite requirement was that one kid said that the ramp had to "lead somewhere," so that it didn't drive you off a cliff or anything. That's awesome.
Then we looked at the actual law.
With your partner, decide which is tougher: our class' law, or the American with Disabilities Act requirements.
What really stood out to me is how much larger our angles are than the actual requirement. It leads me to think that our understanding of steepness on the page doesn't really match up with our physical experience with steepness. This was a nice intellectual way to realize this, but we should probably find a more visceral way of experiencing it.