Balancing a broom - QI: Series K Episode 9 Preview - BBC

#bbc

[ninjabluefyre]

Alan Davies: Defying physics since 2013.

[ImmortalSparrow]

I wonder how many points Alan will receive for defying the 'science elves' =D

[Inlelendri]

I wonder when Stephen will learn that whenever he says 'always' or 'never' in those kind of demonstrations, one of the panel members will more than likely prove him wrong.
Also, ripping up card - <3

[Smudgie]

The tone Stephen Fry takes with Alan Davis in particular is exactly that which a mother uses on a highly strung and spoilt child.

[dlcipher]

My favourite thing about this show is how, every time Stephen/Sandi asks the panel to do an easy trick, Alan will invariably muck it up. But if he asks them to do something to prove that it's extremely difficult or impossible, Alan will get it right on the first try.

[Captain-Jinn]

Alan, we've always made jokes about how you could totally be the chimney sweep in Mary Poppin's. You're not helping your case, mate.

[bluepalmer]

Absolutely lost it at that cut to Alan at 1:46

[dawnqwerty]

"Perhaps it will look more natural in yours"

[Calvero]

I learned that trick years ago in science class, though we used rulers...less dangerous ;)

[justinyau]

you could say this is a bit of a Slapstick Comedy ;)

[JK-vpux]

No Jo, women all over the country aren't using those to sweep floors. Those are rough brooms designed for outdoor use. Especially good for use on cobbles. Used to sweep streets.

[Tricorvus]

did anyone else come to watch this, in hopes that it would help them with their Quidditch balance? It actually did help me understand something :D

[byheavenlyhosts]

I'm just studying center of gravity...very interesting and funny!
Please do it with a person!

[tomevans]

has anyone else just tried this with the nearest broom they can find?

[CyrusHalcyon]

Isn't this dependent on the coefficient of friction, whereby it won't work if you apply oil to your hands prior? It also obviously wouldn't work in outer space. It would also not work for a very long broom that is several meters long since the angle of incidents and the base coefficient of friction would result in a k_1 (left) and k_2 (right) that are fairly close to k_base such that you would move linearly despite a still non-negligent weight distribution difference once at final position. To that point I'd be surprised if it would work with a plastic broom - given the highest friction? Has anyone confirmed? Wood is very smooth.

[David_B_Dornburg]

Sweaty hands will defeat it. Dry hands will work every time.

[Observer]

The 'science elves' are not as science-y as they should be. It is just *harder* to balance when the CG is low than high because the low CG allows the top to move off center more quickly requiring faster correction reflexes. Plus, with bristles down on the hand, it allow a little torque to be applied even if Alan didn't realize it, but I suspect he did because he hardly appeared to be providing any corrections at all.

[demos]

Because the picture of Archimedes they use shows him with a very big and thick beard.

[ck]

I will watch this episode just for Marcus

[Observer]

It relies on the (coefficient of) friction being PROPORTIONAL to pressure.
The hand nearer to the CG is supporting more weight and has more frictional force so won't move/slide when a given force is applied to pull the hands together. The heavier side 'sticks'.
...
Alan initially fails because he goes too fast and the sideways inertia of the broom holds it in place while his hands move to the center of the length.
...
Danny fails because he is jerking his hands also allowing the sideways inertia to prevent proper sliding of hands.
...
The elves and Stephen aren't quite as science-y as they think... wannabees...