Cam somebody explain the physics behind this trick?

[Argo]

http://www.break.com/index/awe...thpick-fork-trick.html

 

[destrekor]

wtf? how?
i'm still trying to figure out how it was balanced with the toothpick before it was even lit on fire. the end result only further confuses me.

 

[Argo]

I think the balancing works because the center of gravity of the contraption ends up being inside of the semi-circle formed by forks (because of the handles).

 

[MrPickins]

The center of gravity of the whole fork system is at the rim of the cup.

Edit: Argo beat me to it. (And explained it better )

 

[MrPickins]

Doh! meant to edit, not post.

 

[TheGizmo]

Originally posted by: destrekor
wtf? how?
i'm still trying to figure out how it was balanced with the toothpick before it was even lit on fire. the end result only further confuses me.

 

[dpert1]

yeah, the center of gravity is exactly on the edge of the cup, hence why it balances, burning away toothpick doesnt change it by much and as long as the center of gravity remains unburned, it is still balanced

 

[arrfep]

I liked the Against Me in the background. The way I learned this trick was to take a salt/pepper shaker, and stick a toothpick so it's pointing straight up. Then do the same thing with the forks and another toothpick, and you can balance the whole thing tip-of-toothpick to tip-of-toothpick at a right angle. Hard to describe, but IMO much more impressive.

 

[gururu2]

the cup has to be weighted with water for proper support. the weight of the forks is distributed and highest at the ends of the forks due to the curvature. the toothpick just serves as a displaced fulcrum. the toothpick has nothing to do with counterbalancing the weight.

 

[Argo]

The part I don't get is why did the toothpick stop burning exactly at the edge of the glass?

 

[MrPickins]

Originally posted by: Argo
The part I don't get is why did the toothpick stop burning exactly at the edge of the glass?

The cup acts as a heatsink. Take the heat out of the reaction, and it can no longer sustain itself.

 

[Mrvile]

You guys never had those toy birds that would balance on your finger by the beak and "float" in the air?

 

[aplefka]

That's effing nuts. The ad I got was weird too.

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[MrPickins]

Originally posted by: Mrvile
You guys never had those toy birds that would balance on your finger by the beak and "float" in the air?

I had forgotten about those.

http://physics.bu.edu/~duffy/mech/1J20_46.html

 

[mobobuff]

Originally posted by: arrfep
I liked the Against Me in the background. The way I learned this trick was to take a salt/pepper shaker, and stick a toothpick so it's pointing straight up. Then do the same thing with the forks and another toothpick, and you can balance the whole thing tip-of-toothpick to tip-of-toothpick at a right angle. Hard to describe, but IMO much more impressive.

That's also how I learned it, I remember doing it when I was 10 years old.

 

[Squisher]

Originally posted by: Argo
The part I don't get is why did the toothpick stop burning exactly at the edge of the glass?

You ever see anybody boil water in a paper cup? It can be done because the water acts like a heat sink in this instance too.

 

[JackBurton]

Originally posted by: gururu2
the cup has to be weighted with water for proper support. the weight of the forks is distributed and highest at the ends of the forks due to the curvature. the toothpick just serves as a displaced fulcrum. the toothpick has nothing to do with counterbalancing the weight.

Exactly. I didn't even think it was a good "trick." After he burned the toothpick I was saying, "Yeah, and?"

 

[dpert1]

i thought it was creative

also enjoyed against me!

 

[91TTZ]

Originally posted by: MrPickins

Originally posted by: Argo
The part I don't get is why did the toothpick stop burning exactly at the edge of the glass?

The cup acts as a heatsink. Take the heat out of the reaction, and it can no longer sustain itself.

That's not why. It wasn't burning very well to begin with, and when it got to the cup it couldn't get enough oxygen from underneath. Stainless steel has poor thermal conductivity anyway.

 

[Agentbolt]

Originally posted by: JackBurton

Originally posted by: gururu2
the cup has to be weighted with water for proper support. the weight of the forks is distributed and highest at the ends of the forks due to the curvature. the toothpick just serves as a displaced fulcrum. the toothpick has nothing to do with counterbalancing the weight.

Exactly. I didn't even think it was a good "trick." After he burned the toothpick I was saying, "Yeah, and?"

It's not supposed to be a fucking magic trick, it just looks cool to 99.9999% of people out there who don't have to pick apart something that looks vaguely neat with nerdy physics.

 

[MrPickins]

Originally posted by: 91TTZ

Originally posted by: MrPickins

Originally posted by: Argo
The part I don't get is why did the toothpick stop burning exactly at the edge of the glass?

The cup acts as a heatsink. Take the heat out of the reaction, and it can no longer sustain itself.

That's not why. It wasn't burning very well to begin with, and when it got to the cup it couldn't get enough oxygen from underneath. Stainless steel has poor thermal conductivity anyway.

Yeah, lack of oxygen was definitely a large factor. I'd still bet that the mug absorbed enough heat to play a role, though.

 

[Kelvrick]

Originally posted by: Agentbolt

Originally posted by: JackBurton

Originally posted by: gururu2
the cup has to be weighted with water for proper support. the weight of the forks is distributed and highest at the ends of the forks due to the curvature. the toothpick just serves as a displaced fulcrum. the toothpick has nothing to do with counterbalancing the weight.

Exactly. I didn't even think it was a good "trick." After he burned the toothpick I was saying, "Yeah, and?"

It's not supposed to be a fucking magic trick, it just looks cool to 99.9999% of people out there who don't have to pick apart something that looks vaguely neat with nerdy physics.

Aren't magic tricks basically either illusions or manipulating the audience's point of view through the use of physics/chem?

 

[0roo0roo]

yea heatsinking.
steel wool burns cuz its increased surface area. block of steel has too much heatsinking to burn

 

[mobobuff]

Originally posted by: Agentbolt

Originally posted by: JackBurton

Originally posted by: gururu2
the cup has to be weighted with water for proper support. the weight of the forks is distributed and highest at the ends of the forks due to the curvature. the toothpick just serves as a displaced fulcrum. the toothpick has nothing to do with counterbalancing the weight.

Exactly. I didn't even think it was a good "trick." After he burned the toothpick I was saying, "Yeah, and?"

It's not supposed to be a fucking magic trick, it just looks cool to 99.9999% of people out there who don't have to pick apart something that looks vaguely neat with nerdy physics.

You can't expect a forum full of nerds to not pick apart the trick with logic. Logic makes them comfortable, and it irritates them when others do not understand something that seems so simple to them.

Still I think the trick is cooler when used with two toothpicks, one horizontal and one verticle. A slowly burning toothpick just takes focus away from the really cool part.

 

[mobobuff]

Originally posted by: 0roo0roo
yea heatsinking.
steel wool burns cuz its increased surface area. block of steel has too much heatsinking to burn

Your post reminded me of this video. There are other videos with more action, but this one has Johnny Cash.

Yaaaay!