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Spanglefish Gold Status Expired 20/09/2014.

Physics of the Hula Hoop

Visitors to the Inverness Floral Hall on Saturday 8 November were able to see amongst the flowers and greenery a swirl of yellows and blues and reds as hula hoops swung steadily round and round, to the sound of the water falling into the pool.

Was it an effort to recreate the sights and sounds of the South Seas? Not quite, although there was that kind of feeling in the air. The real purpose was to earnestly explore The Physics of the Hula Hoop, under the guiding sway of Trina Dinnis.

Trina Dinnis writes:

I started going to a hula-hooping class a little over a year ago. For me it was the perfect combination. It involved periodic motion, and I do like a bit of periodic motion, phases, frequency, all that stuff I'm very keen on.

It is a sort of dancing thing, some people dance beautifully with their hoops, though unfortunately I'm not one of them, but I am very keen on dancing, and it is also slightly ridiculous, and everyone should do something ridiculous now and then. And to answer the obvious question, yes, I can tap dance and hoop at the same time, but not terribly well.

Not long after I started going to the class, I became curious about how they were made, so I followed instructions on the internet and made myself a hoop. But I still didn't quite understand what was going on there. Especially I didn't understand why it was easier to hoop with larger heavier hoops. I researched this on the internet, but couldn't find a truly satisfying answer. I think I sort of understand it now, but I still haven't completely sorted out everything. It's much more complicated than I anticipated.

I thought I would talk about the mechanics of the hoop motion for a few minutes, then I could move on to less obvious things associated with it (I would have really loved to get in an explanation of FM radio in there) but in fact it’s too complicated for that – at least it is for someone like me.

What astonished me was that investigating the physics of circular motion and spin, lead to me discovering how to control my hoop better, especially when hooping on my hands. I mean, rotating the hoop on my hands, not when doing a handstand. Some people can do this, but I'm not one of them. I dream one day of hooping when doing a headstand, but that happy day is still far far away, alas. Unfortunately I don't think I dare demonstrate hand hooping during my talk, because hoops have a tendency to fly off, and this might be a bit dangerous.


Trina is an electronic engineer by training, with experience in research and industry which ranges from aspects of wireless networks to designing and testing computer hard drives. She has a particular interest in communication of science, and was encouraged to develop her skills in this through the NESTA Crucible programme. She is involved with Girls Get SET, a scheme to encourage women to study engineering.

You can find out more about her hula hoops at her own hula hoop site:

During the Festival, Trina also spoke on The Mathematics of Why I Don't Have a Boyfriend. She was featured on the BBC website: Engineer to reveal Hula Physics.

Click here to go to the main programme page

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