Angular Momentum Demo: Hoberman Sphere

This is a demonstration of the conservation of angular momentum using a Hoberman sphere, a plastic sphere frame that can be contracted by pulling on a string. Pulling on the string while the sphere is rotating causes the sphere's moment of inertia to decrease and its angular speed to increase, demonstrating conservation of angular momentum.

It was created at Utah State University by Professor Boyd F. Edwards, assisted by James Coburn (demonstration specialist), David Evans (videography), and Rebecca Whitney (closed captions), with support from Jan Sojka, Physics Department Head, and Robert Wagner, Executive Vice Provost and Dean of Academic and Instructional Services.

[ejicon]

His smile on his face at the end is priceless.

[ExplosiveBolts]

I already knew what was gonna happen, but I didn't expect it to speed up that fast.

[karldavis]

I like how he did this in 1 minute, 21 seconds, instead of taking 10 minutes for something that didn't need that much time.

[sarmadmaqsood]

I did the same thing on spinning chairs and this revolving chair at a park when I was young. Always fascinated by how contracting the legs makes you go faster. Now I know!

[josephjackson]

This is one thing I didn’t have at my college: actual demonstrations of the theories we were studying.

[Freedom-gezf]

....: He was so happy like kids when he play with toys...
....: That's physics bro,

[Daniel]

The demo is cool, but I was much more impressed with this Hoberman sphere. I've never seen it before and it looks very ingenious.

[drewcipher]

1:07 Have you seen ice-skating? Now that's an impressive example of conservation of angular momentum.

[DiscoFang]

Most spectacular demonstration?? Clearly this man has never spun around on an office chair holding a heavy text book in each hand - with arms extended then pulling the arms in. As a kid it is truly spectacular.

[madmusician]

The world needs more teachers like him! Thank you sir!

[philjamieson]

It's very satisfying to watch. A splendid demonstration. Thanks for putting this on here.

[kandaman]

Now THAT'S a PRETTY COOL Demo of angular momentum.
This guy just explained the concept of angular momentum in less than 2mins. BRILLIANT!!!

[fifaham]

I studied physics in the University 30 years ago and am still studying more, this toy is amazing for it is demonstrating the conservation of M in action - it is truly a precious toy.

[deanwcampbell]

Excellent demonstration of why pulsars spin so rapidly.
Love it, thanks!

[TheDragonCat]

I was a figure skater when I was younger, and still do it sometimes as a hobby. I have felt the affects of "get smaller, spin faster." It's incredibly fun.

[random_human_]

I am in 9th, I don't even know about conservation of angular momentum but I found this amazing

[massiveheadwoundharry]

Any kid that's played on a playground tire swing understands this.

[battlefieldclips]

This is how you should learn science. Not just remember the words or statements.

[sezja]

This made the concept so clear i want to cry

[aliyyanurr]

wow, i need this for my video explaining angular momentum conservation in core-collapsing star (massive big star contracted to very small neutron star). thank you for the video and the Hoberman sphere!