Why Do Things Spin? - with Hugh Hunt

Why does a spinning top stand up? Why doesn't a rolling wheel fall over? And how does a falling cat always manage to land on its feet?

From topspin in tennis, to angular momentum in ballet dancers, to satellites in space, spinning things are strange.

Hugh Hunt explores the common underlying threads that link all of these interesting phenomena, using examples ranging all the way from boomerangs to cats in this talk for our family programme.

Hugh Hunt is a Reader in Engineering Dynamics and Vibration at Cambridge University. His research centres on the control of noise and vibration from underground railways. He is now promoting other technologies for the removal of non-CO2 greenhouse gases and also runs the Cambridge Climate Lecture Series which aims to raise awareness of the urgency around climate change.

This talk was filmed in the Ri on 7 February 2020.

---

A very special thank you to our Patreon supporters who help make these videos happen, especially:
Alan Latteri, Andrew Downing, Andrew McGhee, Anonymous, Dave Ostler, David Crowner, David Lindo, David Schick, Greg Nagel, Jan Bannister, Joe Godenzi, John C. Vesey, Kellas Lowery, L S, Lasse T. Stendan, Matt Townsend, Osian Gwyn Williams, Paul Brown, Rebecca Pan, Robert Hillier, Robert Reinecke, and Roger Baker.

---

Product links on this page are affiliate links which means it won't cost you any extra but we may earn a small commission if you decide to purchase through the link.

[TheRoyalInstitution]

Tennis, ballet dancing, ice skaters, satellites, boomerangs, gyroscopes and - of course - CATS! There's just so many spinning things explained in this video that we can now count our head as one of them, too. As always, let us know what you thought about this demonstration-stuffed talk here in the comments!

[garyhardman]

Made for children. However, as a 60 yr old, with an electrical engineering background, these lectures entertain and educate me. Thank you.

[elmikeomysterio]

I know these are all meant for kids up to about 16, but I'm twice that and get excites every time I see a new upload. Such great presenters explaining complex things simply.

Its a great example of "if you can't explain it simply, you simply don't understand it".

[altareggo]

He's REALLY good with children - supportive, sensitive, responsive, and clear!! An ideal teacher.

[GoldSrc_]

I love these lectures :D.
Thank you Royal Institution for making them available for all of us to watch around the world.

[altareggo]

The Royal Institution is a national treasure!!! It serves educational purposes that no single school or university can easily duplicate, and inspires minds young and old, to become more interested in and to engage in the scientific process on a national and international level. May it last as long as our civilization and beyond!!

[CrippledMerc]

I love the RI lectures. Even as a 30 year old they take me back to the feeling of being in class with one of my favorite teachers growing up, of which there was only a few. I really wish more places did things like this, especially for my future children. Unfortunately there isn’t a place around me that does anything like this which is quite sad because they’re not just great lectures that are fun for kids and adults alike, they actually teach you real science, and how to think scientifically. It’s great stuff!

[DrJeeps]

It's wonderful to see young children attending these science lectures/demonstrations. Well done RI, well done!

[nickname]

That was one of the most entertaining RI lectures for sure. Thank you.

[residentenigma]

23:01
That little affirmation from the crowd, had me laughing for about 5mins.
I wish that kid all the Joy's of life, in return !

[StreuB]

Professor Hunt is amazing. So engaging and so much passion for presenting. From a 42yo engineer from the US, I envy all those children in that audience!!! I would have paid to be there!!! Had a smile on my face the entire time. Wide-eyed laughter and ooh's and ahh's are telltale signs. There are future engineers, scientist, chemists and physicists in that audience!!!

[nHans]

Ah, today, spinning things and things moving around in circles became fun for me once again! Many years ago, I had been badly scarred in college, struggling with moment of inertia tensors, Euler angles, quaternions and what not. However, having graduated, I feel I've earned the right to gripe about a couple of things in the video (with profuse apologies to Hugh Hunt—your lecture remains wonderfully interesting and educational!).
16:14—When Zoë puts her arms out holding the weights, they feel heavier than when she holds her arms in. That's simply because the weights exert a greater _torque_ on her shoulders when her arms are outstretched. It's not because of the change in her "angular mass", which the slide says at 16:42.
26:33—Hugh demonstrates the _Intermediate Axis Theorem_ aka _Dzhanibekov effect._ I think, however, the children in the audience are too young to appreciate its significance.

[crazypj]

I remember seeing my first RI Christmas lecture around 1975 on black and white TV
That was also about centrifugal/centripetal force when there was only a single scientist worldwide studying the 'gyroscope phenomena' and a lot less known about it.
Edited, Didn't watch bit where he mentioned Eric Laithwaite, 1976 until later

[brotherstech]

This lecture was brushing up what I already knew. However good for kids👶.

[brianwheeldon]

Loved the talk and children's participation Hugh, excellent... exemplifies one of the many very good reasons we need to organise our climate crisis response urgently. Thanks again.

[clivewells]

That was the most edjutaining lecture I've ever seen!

[daveshaw]

Just think how many of those kids will be changed forever by this lecture, pursuing careers in science because of it

[rhbofwcc]

You're having too much fun and we are learning so much. Great job.

[toodgs]

It has always puzzled me how planetary systems stay together, but add spinning forces to the problem and it all changes. No doubt I should have read more books. Most informative and well presented, I have recommended it for my grandchildren.

[tesconstamylo]

I wish I had this guy for a physics teacher!!