How to Run Up a Wall

I’m sure most of us have seen some form of wall-running in movies or films, but if not, there’s a link to a video below. The person in the video appears to walk up between two walls by jumping from one wall to another. I want to explore the physics behind how this is possible. 

The physics concepts being applied here are friction and momentum. The force of friction acts on the person when he is in contact with the wall. The equation for friction is
Ffr = μsFN 
where μs is the static friction coefficient and FN is the normal force. There is a change in momentum (product of an object’s mass and velocity), which is also known as impulse (change in an object’s momentum) when the person is jumping towards and away from a wall. Impulse occurs when there is a force acting on an object for a certain amount of time (product of the force applied to an object and the amount of time it is applied). The equation we are using is 
Δp = F/Δt
where F is the force applied to the object and Δt is the change of time. The force being applied in this situation is the force from the wall. Using Newton’s 3rd Law, when the person pushes against the wall he is applying force to the wall, the wall pushes back on the person with a force that is opposite but equal in magnitude to the force from the person. The person can only exert force on a wall for a short amount of time, so to maintain the momentum, he changes direction and pushes against another wall using the force the first wall exerted on him. As he repeats this action, there is a net upward force that allows him to go up the two walls.

The diagram gives a visual illustration of what’s happening featuring stick figures and a wall represented by a gray rectangle. 

References

https://www.wired.com/story/how-to-run-up-a-wall-with-physics/
https://www.youtube.com/watch?v=23QOy9Q2qNI&feature=youtu.be
0:07 - 0:12