Flight of the Pole Dancer

The laws of physics apply to all

PolegirlWelcome to PopSci's newest blog feature, "The Breakdown." Each week, we'll pick a Web video that involves a minor crash, explosion or other nonfatal mishap and invite one of our experts to explain, in scientific terms, what went wrong. In this week's edition, physics whiz Michael Moyer analyzes the case of the tumbling pole dancer...

Newton’s First Law of Motion states that bodies in motion tend to stay in motion. The same holds true for rotating bodies and, as we see in this video, doubly true for rotating, gyrating bodies.

Consider the body of the body in question. After a quick shake of the head right and left, she leans backward to begin her rotation around the pole. Her pivot points include her right hand, held fast to the pole, and her left foot (disastrously clad, we will soon learn, in three-inch heels). She now has a sizeable amount of angular momentum moving counterclockwise around the pole, and this can be halted only by an external force.

Unfortunately for our young dancer, the outcropping of wall her rear end soon encounters does not provide that force. Instead it simply serves as a new fulcrum, shifting the center of rotation from her hand to her hip. This does two things: Like a figure skater pulling her arms in, shifting the center of rotation closer to her center of mass acts to speed the rotation up. More important, it also means that her right hand must begin to rotate around the wall as well.

The outcome is predictable. A hand rotating away from the pole cannot continue to hold onto the pole, and without that grip, our dancer loses her balance in a most sudden and undignified fashion. Lesson learned: Newton can still represent. Can you think of a YouTube video you'd like explained? Send us a link in the comments section. —Michael Moyer

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*The embedded video that used to live here was removed from YouTube because of copyright silliness. But you can still see it at Break.com*

47 Comments

Comments

HumanGame (imp...
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One thing I would add, the probable influence of alcohol to our subjects lack of balance and it's aid to Newtons first law in this matter.

Keep the "Breakdowns" coming.

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Larian LeQuell...
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Assuming her to be a petite young woman, what sort of strenth would she have to posses in her hand (and arm) to actually manage to hold on to the pole? Let's say she weighs 110 lbs?

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Tonik (imported)
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The figure skater reference is bullshit.

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Brit (imported)
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This is a great idea for a web series. Love it.

But she fell because of Murphy's First Law of Drinking... never drink so much that you lose your grip on the planet, or something like that.

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Wang Junyu (im...
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Have a question. Why you said this event is like a figure skater pulling her arms in? In the video when the dancer changed her fulcrum, the velocity remained constant, not the angle momentum.

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Tarantulas (im...
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"The figure skater reference is bullshit."

Great job backing up your statement! You should totally write for "No one cares what you think" magazine!

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Modern Polymat...
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The video was funny. This, on the other hand... not so much.

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yatpay (imported)
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Great idea! I've often wondered what happened in a lot of online videos.

I'm pretty sure I know what happened here, but it still might be good to write about: http://www.youtube.com/watch?v=_uEyhEcZLG0

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Dondee (imported)
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Assuming her to be a petite young woman, what sort of strenth would she have to posses in her hand (and arm) to actually manage to hold on to the pole? Let's say she weighs 110 lbs?

Well if she was not as petite and had more mass and proportional arm strenght for her size, and afer observing the flexing of the pole and the shape of the pole, I would think she may have been able to pull the pole down with her.

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Anonymous (imp...
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Please explain this:
http://www.youtube.com/watch?v=S1HBuAduTo0

What the hell went wrong?

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