This makes my head hurt

[andrewducker]

Because it's having the same effect on my brain as one of those optical illusions that's both a rabbit and a duck.



Half the time I'm thinking "So, the centre of gravity is under the bit of ruler that's on the ledge, so it stays perfectly still." and half the time I'm thinking "But the weight is being applied on the right hand side, so at the least it should apply a rotational force" and the the third half of the time I think "But the end of the handle is pressing back against the ruler, which could counterbalance that".

And then my head just hurts.

Anyone who has a hammer, a hairband, a ruler and a shelf handy care to replicated it, video it, and stick it on youtube?

Comments

[ggreig]

I have done this and will be able to upload the video this evening.

[andrewducker]

I tracked one down, and posted a link to it on the LJ side. But it sounds like a fun project!

[ggreig]

Ah well. I posted the video anyway because a) it's a cool trick and b) why not? :-)

[darkoshi]

nifty!

[andrewducker]

Oh, wait, someone did:

[drjon.livejournal.com]

Someone's been dividing by zero again!!!

[drdoug.livejournal.com]

Don't have a video, but have just replicated it with a metal ruler, claw hammer, and a loop of string. Takes a little bit of fiddling to get it balanced just right, but it works for me. One key thing to get right is that the heavy bit of the hammer is well beyond the edge of the ruler.

I think one's physics intuitions are led astray by seeing it as three separate components. Imagine it's solid, and it doesn't seem particularly bizarre.

[andrewducker]

Yeah, I ended up thinking of it as a curved object, and that worked for me.

[drdoug.livejournal.com]

Once you've done it, you can lift it off the table/shelf and balance it on an outstretched finger held horizontally, perpendicular to the ruler as seen from above (making a T-shape). Assuming, of course, that your outstretched finger is strong enough to hold up the hammer.

I can't decide whether that looks more mind-bending or not. Possibly more spooky to the audience, but less to the person holding it, because you can really feel that the CoG is directly under your finger by rolling your finger a little bit either way.

[skreidle.livejournal.com]

And while it really is three separate components, the forces on each part hold them in place.

As for the whole assembly, it acts like a bent pendulum; it'll sit statically with gravity acting on a straight line through the supporting point and the center of mass (in or near the head of the hammer). So long as that arrangement has the supporting ruler sitting level or tipped up a bit, it won't fall. :)

[channelpenguin.livejournal.com]

seen as a "one object" it looks to me a lot like a handheld steadicam... (we have 2 in the house though not this one)

http://www.tiffen.com/handheldmerlin.html

[danieldwilliam.livejournal.com]

This is going to impress the heck out of my 14 year old daughter.

[avatar.livejournal.com]

If you want to impress a teenager with this kind of stuff, here's another one:

Make a small paper box/container, and put some water in it.

Then light the paper on fire from the bottom. It won't light up.

[original-aj.livejournal.com]

I remember constructing a parrot at school that was similar - it was a silhouette cut out of cardboard with a plasticine weighted tail and it would balance on a finger. This is a similar idea

[drdoug.livejournal.com]

Ah! I *knew* I'd seen something similar before. Thank you.

[original-aj.livejournal.com]

No problem! ;)

[holyoutlaw.livejournal.com]

Here is a large number of similar images, from the "Equilibres" series by Peter Fischli and David Weiss.

Balancing a hammer

[livejournal.livejournal.com]

User drdoug referenced to your post from Balancing a hammer (http://drdoug.livejournal.com/237480.html) saying: [...] the centre of gravity is directly under the end part of the ruler. As mentioned in the comments [...]

[drdoug.livejournal.com]

Just posted myself - here's the YouTube video of my version:
http://www.youtube.com/watch?feature=player_embedded&v=BwbPwstyhdM