(Science background: A pendulum has a resonant frequency and will swing noticably higher if 'driven' at or near its resonant frequency. The resonant frequency varies with the length and weight of the pendulum).

I was walking behind a woman earlier today whose ponytail resonant frequency and walking cadence were so perfectly correlated that her (large) ponytail swung left and right up to the horizontal with each step she took. This then is an idea for a device (or perhaps an add-on function for an existing device, such as a pedometer) which will use as input parameters data on your walking cadence and the length and weight of your ponytail and sound an alarm if you are in danger of approaching a walking cadence/ ponytail resonance synchronisation. You can then take remedial action, such as walking faster or getting a haircut.
-- hippo, Jul 30 2007

Suit of swing Suit_20of_20swing
As a ponytailless pedestrian, jealousy has inspired invention. [Worldgineer, Jul 31 2007]

they're great as weapons if you swing around fast enough.

I'm not quite sure what you're getting at here, h.

btw did you ever see the pic I posted for you over at M?
-- po, Jul 30 2007


I thought they always bobbed in resonance?
-- DrCurry, Jul 30 2007


[po] sorry - missed that
[bigsleep] Yes, good point. Perhaps this should be repurposed as a device to allow the wearer to maintain a chosen level of ponytail resonance with their gait.
-- hippo, Jul 30 2007


[Fuzzy Logic]: It's the length of a pendulum that determines it's frequency, not it's weight. (At least that's what I remember...?)

<useles fact #5302>The classic c64 game Yie Ar Kung Fu II had an enemy called Yen Pei and his special weapon was his Iron Pigtails.</uf>
-- Jinbish, Jul 30 2007


pointless and stupid (make that daft actually) = my total approval +
-- xenzag, Jul 30 2007


Actually, by choosing a pace at one's ponytail resonant frequency, kinetic energy could be stored in the ponytail, which would then be imparted to the walker on the next swing.
-- bungston, Jul 30 2007


If the wearer wore two of those bobbly- things in her ponytail, one near the end and one somewhere mid-way, then the ponytail would become a complex pendulum and would not have a resonant frequency.
-- MaxwellBuchanan, Jul 30 2007


/It's the length of a pendulum that determines it's frequency, not it's weight/

It's both.
-- Texticle, Jul 30 2007


//It's both.//

No, it isn't. At least for a classical pendulum, the weight on the end of the string has no effect on its frequency.

Simple gedanken experiment to prove this: set up two identical pendula side by side and set them swinging in synch. Now add a drop of liquid glue between the two bobs as they swing side-by- side. Do they change speed? Of course not. Now let the glue set. Does this change their speed, of course not. Now replace the two adjacent strings with a single one of the same length. Does this change the speed? No. So you have doubled the mass of the pendulum without altering its frequency. QED.
-- MaxwellBuchanan, Jul 30 2007


I stand corrected. The mass term cancels out for a simple pendulum.
-- Texticle, Jul 31 2007


Nice gedanken experiment [Maxwell] - for some reason I can't clearly remember though, the "simple harmonic motion" equations only work for pendulums with very small amplitudes. For a violently swinging ponytail, I think mass does come into the equation.
-- hippo, Jul 31 2007


Actually - you might be right. My old high school physics project was to measure small 'g'. To do so most effectively I suspended a pendulum the entire height of the stair well (4 stories). If I remember correctly, this was to minimise the approximation based on trig. of triangle vs circular arc.

Somewhere, mass did come in to the equation.

I'm thinking that we're in danger over analysing here.

<tabloid scandal>
Halfbakery in pointless pedanto-science SHOCK! - Pictures inside
</tab scandal>
-- Jinbish, Jul 31 2007


I think mass stays out of the equation (I suppose at some point one of us should look it up). Go back and re-read [Max]'s comment, but replace it with a big swing.
-- Worldgineer, Jul 31 2007


I always thought they did this on purpose.
-- GutPunchLullabies, Jul 31 2007


+ as long as I can have bells attached...
-- xandram, Jul 31 2007


//Somewhere, mass did come in to the equation// Mass becomes relevant in two contexts:

(a) when factoring in "losses" such as air resistance or friction at the pendulum's pivot etc. In these cases (and particularly when the swing is large), small masses are proportionally more affected than large ones.

(b) when the mass of the "bob" is small compared to the mass of the "string". The simple calculation assumes that the string (or whatever) has negligible mass; again, this doesn't work when the mass of the bob is very small.

For a ponytail, it is indeed more complex. The mass is distributed along its length rather than at the end; the ponytail is flexible to an extent; and the root of the ponytail is pretty much fixed in one direction (determined by the direction of hair growth and the way the ponytail is gathered). In some respects, therefore, the ponytail is midway between a simple pendulum and a ruler twanged on the edge of a desk.
-- MaxwellBuchanan, Jul 31 2007


Period of swing (simple pendulum) is two pi root L over g. (the mass cancels out from the equations that you have combined to get this one.) But, whilst I agree that the classic three-plait pony tail is a complex pendulum in theory, the fact remains that it will have a resonant frequency resulting in the effect that so disquieted hippo. Personally it is not a problem from which I suffer (disquiet - not resonance, though not that either) and so I welcome any inventions that make body parts swing wildly and discourage any that aim to prevent same.
-- Karnuvap, Aug 01 2007


Picturing a flouncing ponytail, it seems in my mental simulation that is is more like a continuously cracking whip (Split ends whistling with speed, roots clamped tight under elastic) than a pendulum, probably because the weight is evenly distributen.
-- GutPunchLullabies, Aug 01 2007


//because the weight is evenly distributen// Das ist eine Deutche geponytailen, nein?
-- MaxwellBuchanan, Aug 01 2007


The German for ponytail is even better that that: "Pferdeschwanz" (according to Babelfish).
-- hippo, Aug 02 2007


Bun for the notion, even though I like it when my ponytail and gait synchronize in a way that (some might consider positively preposterous but) makes me feel positively Marlo-Thomas-ish.
-- Libertine, Aug 02 2007


It occurs to me, a frequent ponytail wearer, that the way to quickly dispell the pendulum effect is to simply lower the ponytail on the back of your head. If it bothers you so much. I rather think that woman was pretty proud of her high-flying hair.
-- k_sra, Aug 02 2007


Can we harness the power of the ponytail? Perhaps a ponytail-powered gym?
-- pigtails_and_ponies, Aug 05 2007



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