Date: Tue Aug 18 19:53:29 2009 Back to Contents ------------------------------------------------------------------------

Author: Irons, Stephen

Subject: Re: jumping disks


I just got some today too. I found that some of them were on a bit of
a hair trigger at first but after using them a few times they broke in
a little bit.

I also put one relaxed on a hot plate, label side down and was
satisfied to see it pop just as vigorously as it expanded from the
heat than it does when it cools. I think this proves that it's
bimettalic right?


On Aug 18, 2009, at 4:50 PM, "Urs Lauterburg" wrote:

> Chuck,
> I don't see a ''dimple'' in the center of the disks. In fact they are
> pretty small in diameter (about an inch or so). In fact you don't see
> well that they buckle a bit. Now, in this hot summer I can just take
> one into my hand for a moment, then bend it the ''wrong'' way and set
> it on a table. After 10 seconds or so the disk would take off. OK,
> they only go up well if the hollow side is facing the table to give
> it a center push when the disk suddenly bends. Why do the disks jump
> higher when released on a penile? Is it because of the low air
> pressure which sticks the disk a bit to the surface?
> Anyway, again a simple demo but quite a number of aspects to consider.
> Regards
> Urs
> Urs Lauterburg
> Physics demonstrator
> Physikalisches Institut
> University of Bern
> Switzerland
>> If these 'new' ones have a small 'dimple' poking up in the center -
>> try this -
>> Carefully balance the warm (cocked) disk on the point of a pencil
>> NOW measure the height of the jump!
>> This effect also works with the more mundane rubber poppers.
>> Set the eraser end on the pencil on a table top for stability.
>> On Aug 18, 2009, at Aug 18(Tue) 3:21 , Urs Lauterburg wrote:
>>> Zeke,
>>> Me too I have ordered a sample batch and got it a few days ago.
>>> They seem to come from Sweden (not to be confused with
>>> Switzerland). It seems as if somebody there has found out how to
>>> make these things again. Mine seems to work OK. They jump about
>>> 70cm or so. Did the old ones also jump about that high?
>>> Nice little surprising things and a neat demo too
>>> Urs
>>> Urs Lauterburg
>>> Physics demonstrator
>>> Physikalisches Institut
>>> University of Bern
>>> Switzerland
>>>> I received the jumping disks in the mail a couple of days ago
>>>> (they may have come sooner but I was out of town).
>>>> They work as advertised with the caveats listed on the website.
>>>> They are fairly small and they have sharpish edges. They are
>>>> fairly stiff and take some push to get to pop. In chilly San
>>>> Francisco, it takes a long time to heat them up enough for them to
>>>> hold their "loaded" position. I found that by keeping them in my
>>>> pocket, they would be close to being warm enough without waiting
>>>> an excessive time for them to warm up enough.
>>>> I think that the rubber poppers probably teach conservation of
>>>> energy better, but metal discs are more interesting in a material
>>>> science kind of way.
>>>> Zeke Kossover
>>>> PS I also bought the Beta Pen
>>>> which is a
>>>> pencil that uses metal rather than graphite as its writing medium.
>>>> As a novelty it succeeds and might make an interesting material
>>>> science presentation, but it is a rather unpleasant writing
>>>> experience.
>>>> ----- Original Message ----
>>>>> From: "Marc "Zeke" Kossover"
>>>>> To:
>>>>> Cc:
>>>>> Sent: Thursday, July 30, 2009 3:48:06 PM
>>>>> Subject: Re: [tap-l] jumping disks
>>>>> From: Marsha Hobbs , sent: Thursday, August 31, 2006 7:18:02
>>>>> PM
>>>>>> A few years ago we gave away jumping disks at science
>>>>>> presentations. I seem to recall they were from Edmund. Are
>>>>> they available
>>>>>> anywhere these days?
>>>>> Yep, you are reading the date right. Marsha asked about jumping
>>>>> disks three
>>>>> years ago. As I recall, we didn't find any suppliers for her. As
>>>>> I was wandering
>>>>> around, I found some for sale at Grand Illusions, the fun Brit
>>>>> toy site
>>>>> I ordered some
>>>>> today and am waiting patiently for them to come in.
>>>>> Marc "Zeke" Kossover

From Tue Aug 18 19:53:29 2009