Physics & Breakdancing
Break dancing, a.k.a breaking, b-boying, or busting-your-face is a type of dance usually associated with hipsters in urban cities. Even though it seems these dancers are only concerned with “funky music” and “bustin’ moves”, they are actually hardcore physicists whose muscles are performing high-speed physics calculations.
Momentum: the force residing in a moving object, due to the mass and speed of that object. Momentum is calculated by multiplying a body’s mass with its velocity
To change momentum you must apply force
Change in momentum= force times duration of time the force was applied
Angular Momentum: the angular velocity times the inertial moment of an object moving along a circular pathway; gives us an indication of how hard it is for an object to stop.
· Angular velocity= how fast an object spins
· Rotational Inertia =inertia of a rotating object
Torque: the rotational force or twist that starts, stops, or keeps a mass moving.
Inertia: the tendency of an object to stay still when already at rest, or in motion when already moving
Main Point: 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 their angular momentum, breakdancers apply torque. In this specific example it is force
acting at a distance from a spin axis. The breakdancer can either push harder or further away from the
spin axis to spin faster. The dancer is able to change their angular momentum by kicking hard and far
away. The particular breakdancing move being analyzed today is called the air flair. It is
simply a variety of changes in angular momentum.
image -step 1
image -step 1
The breakdancer first makes a torque between the floor and his foot by swinging a leg out in front, sideways. The other leg’s foot experiences a torque because the force on the breakdancer’s toes go one direction, and the force on his heel goes another. After completing a torque, the breaker kicks off of his twisting foot and arrives on the floor with both hands. The breaker will next ensure his legs are apart in order to push his hardest against the ground with his right hand. This will provide lift equal to, but hopefully much more than: mg minus the upward force provided by his back-swinging left leg. The breakdancer adds extra lift with his left hand as well as extra rotational inertia by pushing off at an angle. The breaker then attempts to increase his rotational inertia by spreading his legs out as far as he can when they are naturally circling around.
If the timing is right the breakdancer will “pop” into the air, such as in picture 2. Here, the breaker has the force of gravity alone acting, and cannot change his angular momentum. However there is still a way to turn over, despite constant angular momentum. It can be done as the breakdancer changes their rotational inertia (by changing the orientation of their limbs, etc.). Since angular momentum is constant, angular velocity must change correspondingly. Therefore, the breakdancer’s retracting limbs allow him to turn-over to an agreeable angle. If done in the best way, the dancer should provide enough initial lift to reach across and land on his other hand.
image- step 3
The rotational inertia of his rising leg causes a net force upwards, while the other provides a horizontal twist. Lastly the breakdancer must use the rotational inertia of his legs to propel himself into a position similar to picture 1.
1st Video: http://youtu.be/RkWn71XkVB0 ;
2nd Video: http://youtu.be/wx-h57fTuTU ;
Both videos give way more in depth coverage of what break dancing exactly is, and they even talk about specific moves not covered. Very interesting and entertaining-It explains the topic well because they relate physics in an attention-grabbing way.
Faust, Frey. "Axis Syllabus Research Community Portal - The Relevance of Physics for Dancers." Axis Syllabus Research Community Portal - The Relevance of Physics for Dancers. N.p., n.d. Web. 21 Mar. 2013.
Rodriguez, Harold. "Physics of Break Dancing." UP News Online. N.p., Nov. 2007. Web. 21 Mar. 2013.