The Physics of PARKOUR
Entry posted by bazinga818
4,357 views
Parkour, sometimes referred to as "free-running", has always fascinated me. How do they do it? I for one can't even do the simplest of parkour stunts, but I looked into the physics of it a bit, and thought I'd share what I found. 
Of course, these stunts seem scary to us because, frankly, they hurt when we try to do them. Or when I try to do them, anyway. 
In order to make it hurt less and avoid broken bones - to lessen the impact upon landing after a fall, or to decrease the force upon a set of fingers while grabbing onto a wall - it is essential to reduce the acceleration during each collision as much as possible. This relates to Newton's 2nd Law, of course, as F=ma. Increase the acceleration, decrease the force, as there is an inverse relationship between the two.
To do this, one would increase the time of impact by smoothly bending, flexing, or rolling during impact.
Let's apply some of the physics to an example. During impact with the ground, there are essentially two forces acting on your body -- the downward force of gravity (mg) and the upward force of the ground.
Applying Newton's second law we get:
Fnet = Fground - mg = ma
So let's say that I jump from a height of 3.0 meters onto the ground. How much force is the ground going to exert on me during impact?
First, let's apply conservation of energy to determine my speed just before contact.
The gravitational potential energy (mgh) due to my initial height relative to the ground is going to be converted into kinetic energy (½ mv2) just before landing. So
Mgh = ½ mv2
and v = [2(9.8m/s2)(3.0m)]1/2 = 7.7m/s
Now I have to be brought to a stop.
Fground = m(g + a) = m(9.8 m/s2 + a)
We can see that the force of impact depends on the acceleration. But acceleration = change in velocity/change in time and therefore depends on the time of impact. Therefore, if I land on heels and stay stiff, I could be hurt or break a bone. However, if I land on the ball of my foot and bend my knees or duck into a roll upon impact, the time of impact can be increased dramatically. By decreasing my velocity over this extended period of time, the force is substantially reduced.
So there you have it, the physics of parkour. Now I can go apply this and become a parkour beast. 
(Or break my neck. Let's hope for the former.)
Please enjoy the awesome parkour video I found below.
Until next time,
bazinga818 
1 Comment
Recommended Comments