Ok , I was seeing this show on the NAtional Geo. Channel and they discusssing this puzzle.
The puzzle…
You are given a test tube filled about 3/4 with sand , a metal ball is introduced and it settles on the top layer of sand , the tube is then closed. Now the objective was 2 bring the metal ball to the other side of the test tube ( you can’t open it). Shaking the test tube didnt help , did any see the show or does any know how it’s done?
Ps : I missed the answer part cause there was a commercial coming and I had to go out!
I’m guessing k2dave meant that as 3 separate suggestions, nth:
[li]Put a strong magnet on the bottom and shake[/li][li]weightlessness helps too - so bring it along on your next trip to the ISS[/li]Ultrasound could also work
Waverly’s answer should work–it’s why rocks come to the surface of the soil after repeated frost heaves. It’s also a great way to get the good popcorn pieces to the top of the bucket/bowl (shake it–side-to-side seems to work best–and the small bits and unpopped kernels will fall through the large gaps between the big ones, leaving the big ones at the top for you to eat).
They recently did a study on the so-called “Brazil nut effect” where larger pieces surface to the top when shaken, instead of following the logical thought of falling. This effect can be noticed with even the most slight differences in size.
They discovered that sand shaken had 2 ‘currents’ in it, so to speak, one coming up (or down, I forget) from the middle, and 2 going down the sides. This somehow made the larger items rise to the top, no matter how deeply they were buried.
Really though if you take one of those ‘personal massagers’ and hold it against the side of the tube so it makes the sand vibrate it should work. I don’t have a cite for this but I seem to remember an experiment in high school where if you agitated the particles of sand enough it would take on the properties of a liquid. SO that being said if you vibrate the tube, the sand becomes ‘liquid’, the metal ball which I am assuming is more dense than the sand around it will sink to the bottom.
This is known as ‘liquidifaction’ (sp?) and almost always involves water just below the ground - after the Loma Prieta 'quake (SF, 1989), some folks in the neighborhood discovered that there used to be a small pond where their houses sat - the ones on solid/dry sand fared much better.
