Breakdancing, (a.k.a. breaking, b-boying, or busting-your-face) is a dance usually associated with crazy hip-hop kids living in urban cities. While these kids may seem concentrated on the "funk music", with the hippin’ and the hoppin’ (daww), they are actually hardcore physicists whose muscles are performing high-speed physics calculations. Yes, these kids grew up not only learning the laws mechanics, but also finding ridiculous ways to exploit them.

Before we delve into the analysis of one of the most physics-(and death)-defying dance moves of the genre, let’s have a quick rotational inertia review. As you know, angular momentum gives us an indication of "how hard" it is to stop an object: like p = mv (momentum = inertia times velocity), L = I w (angular momentum = rotational inertia times angular velocity). Hence, things that spin slowly (but have large rotational inertia) as well as things that spin quickly (but have small rotational inertia) are hard to stop.

To change your angular momentum, you can apply a torque (here, a force acting at a distance from a spin axis). You can either push harder or further away from the spin axis to make an object spin faster. A breakdancer tries to change his angular momentum by both kicking hard and kicking far away! Let’s examine the breakdancing move "air flair" or "air track", which is just a bunch of changes in angular momentum.

First, the "breaker" generates a torque between the floor and his foot. This can be achieved by swinging a leg out in front, sideways. The foot of the other leg will experience a torque because the force on your toes goes one way, and the force on your heel goes another. Do not attempt on a slippery floor! After generating a torque, the breaker kicks off of his twisting foot and lands on the floor with both hands. See the figure below.



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