Living the Scientific Life (Scientist, Interrupted)

The Two-Fork Toothpick Trick

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This streaming video shows a fun trick that you can use to impress your friends! But seriously, how does this trick work? [2:01]



Awesome Toothpick Fork Trick

Comments

  1. #1 Chris' Wills
    December 12, 2007

    I’m amazed.
    Have to buy some tooth picks and try that.

  2. #2 RNB
    December 12, 2007

    spoiler alert …
    1. Centre of gravity of forks (because of weight of handles) is over the rim, not beyond the edge.
    2. Once the pick has burned, the melted wood/plastic slightly fuses to the rim
    3. There was negligible toothpick weight needed on the inside of the glass anyway, the counterbalancing was because of the fork handles. So burning that bit off made no difference to the balance.
    Sorry if that random hypothesis has spoiled the magic for you ;)

  3. #3 David Harmon
    December 12, 2007

    The angle of view made it difficult to verify (probably on purpose), but my reading is as follows:

    1) The primary fulcrum here is the edge of the cup. The center of the cup is a visual distraction. It’s worth noting that there had to be something keeping that cup from falling over, perhaps a heavy base.

    Now here’s where I get uncertain, but the key is clearly the counterweights at the far ends of the forks.

    2a) If they extend far enough past the cup edge on either side, they could simply be balancing the works on the primary fulcrum. (This is what I couldn’t be sure of from the angle).

    2b) If they don’t reach far enough for complete balance, there’s still another possibility, by introducing a secondary mobile fulcrum where the toothpick supports the forks.

    The inward-leaning handles would tend to rotate the fork assembly toward the cup. If the toothpick is securely enough wedged in there (and strong enough), it could transmit that rotation, and thus the weight of the forks, back to the primary, fixed, fulcrum.

    I think that given this, the handles don’t have to balance the weight of the whole assembly, they only need to keep it from “toppling” away from the edge of the cup.

    You see situations like this when playing with a gyroscope too — with the gyro spinning on its side, you can support the whole thing on a finger under either tip of the axis, because it “doesn’t want to” topple that spin axis.

  4. #4 David Harmon
    December 12, 2007

    And come to think of it, scratch 2a above, as the torque of 2b is needed to keep it from toppling regardless.

  5. #5 Dave
    December 12, 2007

    Uh, nice observations guys, but I think the puzzling bit is why the toothpick stops burning when the flame reaches the edge of the cup.

    I think it must have something to do with how the air flows around the cup as a result of the flame. I wonder if it would still work if the cup had a hole in the side?

  6. #6 Chris' Wills
    December 12, 2007

    Thanks for the information, doesn’t spoil it for me knowing how it may work.
    I’m still going to try it as it looks impressive :o)

    I suspect that the towel might be hiding a magnet to hold the metal cup down and if the toothpick is to melt to the edge of the cup (as RNB suggests as a possibility) plastic seems more appropriate as wood doesn’t tend to melt.

  7. #7 brian
    December 12, 2007

    The toothpick might stop burning when it reaches the cup because the metal conducts the heat away so quickly? That or the toothpick was dipped in water and the person setting it up carefully positioned it so the water line was right on the edge of the glass. :-)

  8. #8 Albatrossity
    December 12, 2007

    Um, there sure is a lot of speculation here. FYI, I’ve done this trick before, and it does not depend upon a metal cup (here’s a version using a glass cup), or a magnet, and the toothpick does not have to be plastic. Clearly the toothpick in this video was wooden; plastic wouldn’t leave a long ash like that.

    I won’t pretend to tell you that I know HOW it works, but I suspect that the center of gravity explanation in #2 above is pretty close to the mark. But I can tell you that is does work, and no trickery is involved.

  9. #9 jim
    December 12, 2007

    I remember this one from college. RNB has it right. We used to use one fork and one spoon, since you can’t always guarantee to find forks that will interlock exactly, but you can always bend the fork tines a bit to grip the bowl of the spoon.

  10. #10 rpsms
    December 12, 2007

    As others have noted, this is legit. There is no setup or trickery involved.

    I’ve been doing this trick for years. My father taught it to me with a fork and spoon. IIRC his explaination had to do with a rotational force. The fork and spoon most definately try to rotate towards the cup, with the handles pointing down.

  11. #11 hal
    December 13, 2007

    I tried this and I couldn’t get the toothpick to go in straight enough to balance. jim, where do you stick the toothpick if you use a spoon?

  12. #12 twoeightnine
    December 13, 2007

    A witch! A witch!

  13. #13 Dangerous Dan
    December 13, 2007

    Most of this trick is not new. I remember it from my youth, some decades ago. The flame is new to me, but the self-extinguishing part is not difficult to explain. As you can see, the toothpick barely burns. When the flame reaches the rim of the metal cup, the metal absorbs so much of the heat that the toothpick cannot continue to burn. The same thing happens if you try to burn a piece of paper held with pliers. There will typically be a little bit of charred but unburned paper sticking out from the jaws. Dip the toothpick in lighter fluid or some similarly highly flammable liquid and you’ll probably see the fire jump the rim.

  14. #14 Cody
    December 13, 2007

    Yeah, this one’s pretty cool. I was doing it 15 years ago with a quarter, but the toothpick and flame are a new twist. Good post.

  15. #15 Stubb
    December 13, 2007

    I learned this trick as a kid many years ago, but with a slight variation: We would take a salt shaker as the base, and insert a toothpick downwards through the centre hole, creating an antennae-like tip. We would then construct the fork structure same as in the video, except with more of a 90 degree angle at their intersection. The toothpick would be inserted as in the video. We were then able to balance the tip of one toothpick on the other! It takes a bit of trial and error depending on the shape of the forks, but it looked even more unbelievable than this.

  16. #16 jim
    December 13, 2007

    hal,

    The toothpick will go near to the top of the spoon, but exactly where depends on depends on the relative weight of the fork and the spoon, and also the angle the toothpick makes with the combined fork/spoon system. The trick is to ensure that some part of the toothpick passes over the center of gravity of the fork/spoon combination.

    I just did it with a fork, spoon and 4.2cm-long wooden matchstick, on the edgs of a fruitbowl. You will find rather bad pics at

    i255.photobucket.com/albums/hh127/jimliving/forkspoon1.jpg

    i255.photobucket.com/albums/hh127/jimliving/forkspoon2.jpg

    i255.photobucket.com/albums/hh127/jimliving/forkspoon3.jpg

    When you find the right balance, the system is rather stable. Not only decorative, but useful; having achieved it, you can balance the toothpick on the tip of a pen and use it to attract a busy barkeeper’s attention!

  17. #17 amywithlemon
    December 13, 2007

    @stubb…

    i did that version too! and YES it is cooler (no offence to this one).

    i also think it’s harder as you really have to have dexterity to balance the toothpicks and the forks… kudos.

  18. #18 Abbie
    December 14, 2007

    Yeah I had to run and try to see if it worked myself. It did. Wheee.

  19. #19 Jeremy
    December 16, 2007

    I happened to have 2 forks, some toothpicks and a cup handy, so I did the trick. Works fine. It reminds me of those eagles they would sell, with outstretched wings that were weighted so the bird would balance on a small point on it’s beak. I guess the toothpick burning is just to make it look cooler.

  20. #20 Angiepants
    December 16, 2007

    Hahaha. Thrash Unreal.