How to Use Physics to Escape an Ice Bowl

I don't know who invented this crazy challenge, but the idea is to put someone in a carved-out ice bowl and see if they can get out. Check it out! The bowl is shaped like the inside of a sphere, so the higher up the sides you go, the steeper it gets. If you think an icy sidewalk is slippery, try going uphill on an icy sidewalk.

What do you do when faced with a problem like this? You build a physics model, of course. We’ll start with modeling how people walk on flat ground, and then we’ll apply it to a slippery slope. There are actually three possible escape plans, and I’ve used this model to generate animations so you can see how they work. So, first things first:

How Do People Walk?

When you shuffle from your front door to the mailbox, you probably ...