I give Rusty a lesson in physics and biomechanics

Rusty was impressed when I managed to walk down the stairs holding his lidless cup of coffee, and so when we got into the car I started to explain to him how it was done. I took the cup of coffee back and held it in my right hand as I drove with my left, and commenced to larn ’im thusly:

“See, you use your hand as a shock absorber. If you set the cup in the cupholder, or you hold it in your hand but put your hand on your lap, then every bump splashes the coffee out because the bumps go straight to the coffee. But if you’re holding your hand up in the air and we go over bumps, like this, you’re holding your hand loosely, and thanks to inertia the cup tries to stay in the same place, so it doesn’t…it doesn’t…a-CHOO!!!”

Then I had to try to figure out how to get Rusty’s coffee cleaned off of my dashboard.