This time, it is another good one from the May 2011 issue. You have a regular plastic water bottle, filled with water. You poke a hole close to the bottom of the bottle, and another hole close to the top. With both holes opened, the water will flow out of the bottom hole. You can stop that by closing the hole on top. See picture
But what will happen if you toss the bottle of water up into the air?
I'll post the answer later, because I'm sure you might want to try this out yourself! :)
Zz.
7 comments:
I love physics puzzles like this!
Though I'm a little confused, when you say to imagine tossing the bottle in the air, this implies that both holes are uncovered during it's flight, correct?
Correct.
Zz.
my first thought is that when you release the bottle from your hand, there will not be a pressure gradient through a column of liquid in the water. therefore the liquid won't flow out, like when you hold it (in the photo)
My first thought was that the jet would cause the bottle to rotate, then the bottle would turn over and a jet would come out the top hole, which would cause the bottle to rotate...
Then I realised that in freefall the pressure driving the jet would disappear.
So my final answer is that I'd expect the water jet to stop (assuming the bottle isn't spinning at a significant rate).
Water won't come out either hole because both the bottle and the water inside are accelerating at the same rate after being released from your hand.
Water won't come out either hole because both the bottle and the water inside are accelerating at the same rate after being released from your hand.
In free fall there is no pressure gradient as rob says, so the water will not come out. Unless you give it spin when you launch it...
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