Sink A Needle
Science brain teasers require understanding of the physical or biological world and the laws that govern it.
How can you sink a needle that is floating in a bowl of water without touching it, dropping anything on it, or shaking the bowl?
Answer
Dish soap! The molecules in dish soap separate the water molecules from each other, and since the surface tension of the water is no longer as great, the needle sinks!
This experiment actually works, the trick is using some sewing thread to lower the needle onto the water.
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Comments
Ozymandias  
Aug 29, 2005
| Clever!   |
sweetime 
Aug 30, 2005
| very cute - i must remember to try this one at home  |
(user deleted)
Aug 31, 2005
| this one i can use in a science fair experiment that is easy. thanks for the idea.  |
irishthistle 
Sep 04, 2005
| Great teaser! I got it, but only because my neice just did this for a science project. |
Pascal
Sep 04, 2005
| I figure that using a magnet to pull the pin to the bottom of the bowl is the only solution. But that is based on my assumption that I cannot add anything (like soap) to the water because I would cause waves. I think adding soap might violate the "rules" of the game. |
mrtickles
Sep 05, 2005
| I agree with Pascal. I came up with the "correct" answer immediately, but rejected it because it seemed to break the rules as written. |
dcoagtss
Sep 05, 2005
| very cool  |
haldir
Sep 05, 2005
| Never thought of a magnet, good idea. |
smegal
Sep 07, 2005
| Good one keep it up |
Sir_Jean
Sep 08, 2005
| I'm with Pascal and them... Is soap legal in this case?? Maybe we should investigate the effects of Psycho kinetics on the structure of water molecules??? And the magnet, didn't think of that one. |
Caim
Sep 09, 2005
| My answer was to put a big magnet underneath the bowl, it should work  |
Kal-El
Sep 30, 2005
| I thought you were going to say something like, "well I never said you couldn't push it down using something that isn't yourself... I just said you couldn't drop anything on it." |
shabz4lyf 
Oct 12, 2005
| yeah the rules state that you cant put anything onto the needle so wouldnt pouring soupy water be against the rules???   |
bookworm91
Nov 09, 2005
| well i thought of a magnet, but i managed to (of course) make my solution 10 times harder than it could be. lol i thought, "get a magnet of the same force (forgot the right word) and literally use magnitice force to 'push' the needle under. gosh. never thought to put the magnet under the bowl. also didnt think of soap. good one though |
rkaaland
Dec 10, 2005
| I thought I would put the pan of water on the stove heat it until boiling causing the needle to sink. Didn't know about the soap! |
haldir
Dec 12, 2005
| Good thinking. Boiling water would also work. |
troy14
Dec 18, 2005
| Cool! |
tarheel
Jan 06, 2006
| Who needs soap? Just suck the water out of the bowl with a straw. |
Warrior_Poet
Jan 12, 2006
| does that qualify as "sinking?" I think not. Anything to break the surface tension works here. There is no rule against making waves, only against touching the needle or shaking the bowl itself. |
haldir
Feb 02, 2006
| It's amazing how many correct answers exist to this teaser. |
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