I don’t know who invented this crazy challenge, but the idea is to put someone in a bowl of ice sculpture and see if they can get out. Check it out! The bowl is shaped like the inside of a circle, so the more you go up the sides, the steeper it gets. If you think a snowy sidewalk is slippery, try going uphill on a snowy sidewalk.
What do you do when faced with a problem like this? He built a physics model, of course. We will start by modeling how people walk on a flat surface, and then apply it to a slippery surface. There are three possible escape systems, and I used this model to make some animations so you can see how they work. So, first things first:
How Do People Travel?
When you shuffle from your door to the mailbox, you probably don’t think about the mechanics involved. You solved that problem as a toddler, right? But here’s what scientists do: We ask questions that no one has ever stopped to ask themselves.
What are you talking about, have you ever wondered why snow slides? Believe it or not, we don’t know. The exact reason is that it has a thin, watery layer on top. But why? That liquid film exists even below the freezing point. Physicists and chemists have been arguing about this for centuries.
However, in order to start moving, there needs to be energy in the movement. This is because changing motion is a form of acceleration, and Newton’s second law states that the net force on an object is equal to the product of its mass and its acceleration (F = ma). If there is acceleration, there must be absolute power.
So what is that force that drives you forward? Well, when you take a step and push off with your back foot, your muscles apply force back to the Earth. And Newton’s third law states that every action has an equal and opposite reaction. That means that the Earth works a forward-pointing energy back at you, which we call opposing energy.
The magnitude of this frictional force depends on two factors: (1) The specific contact factors, which are captured by the coefficient (μ)—a number usually between 0 and 1, lower values are more smooth, less sticky. And (2) how hard these layers are pushed, which we call the normal force (N).
Normal force is kind of a strange concept to physics beginners, so let me explain. Common means perpendicular to the contact surface. It is the upward force that prevents you from falling under gravity. If you are standing on a flat surface, these two forces will be equal and opposite, canceling each other out, so there is no vertical acceleration.
A final note: There are two different types of correlation coefficients. One is when you have two stationary objects, like a beer mug on a bar, and you want to know how hard you can push them before you make them move. That limit is determined by static friction coefficient (μs).
Then, when the bartender slides your cup down the bar, the frictional resistance—which determines how far it goes—is determined. kinetic friction coefficient (μk). This is usually less, because it is easier to keep something moving than to start it moving.
So now we can estimate the static (Ffs) and kinetic (Ffk) friction force:
