General Chat / Honors Physics Project (help!)

This has me so stumped... For my Honors Physics quarter project, we have to build a device that will sink to the bottom of a watertank and then all of a sudden float back up to the top in less then 30 seconds by itself. You are not allowed to help it at all. I have NO idea whatsoever how this is possible?

Anyone got any ideas on how to approach this? I would REALLY appreciate anything. Thanks.

I thought you were only stupid on the internet.

Could you have sensors on the bottom so that when the object lands on the bottem of the tank then the trigger is pressed, a motor start and it goes up. This would depend on the depth of the tank as if it is realy deep and needs to rise within 30 seconds then you might want to think about some kinda air pressure thing.

This is more Deign and Technolodgy but I hope it's helped.

make a small submarine shaped hollow object with a couple small holes in it...then put in some baking soda...when you put it in water it will sink...then rise to the top...

I think I remember this from a toy in a cereal box when I was like 7...im not totally sure but I think thats how it was...

Well, i have some ideas...I need to know more about the rules though. This is what first came into my head (but it could be a bit iffy)

Take a balloon, and tape it to a rock (just so the rock and balloon are toutching, don't wrap the tape around both). Then drop the balloon and rock into the water. HOPEFULLY, the tapes stickyness will fail, and the balloon will come soaring up. Now, this would only work under two conditions: One: the tape must stick long enough..then loose it's stickiness, and two, the rules must allow you to leave something on the bottom.

i'll keep thinking, but this sounds like an urgent problem you have here.

make a small submarine shaped hollow object with a couple small holes in it...then put in some baking soda (might be baking powder...but you can test it)...when you put it in water it will sink...then rise to the top...

I think I remember this from a toy in a cereal box when I was like 7...im not totally sure but I think thats how it was...

lol yup I rember those.

w/o any technology, basically, you need to make the device denser than water as it goes down, then less dense than water when it goes up. One idea is to fill it with something like sand but poke a hole in the bottom of the container. Make it bottom heavy too, but hold it upside down until you drop it. Theoretically, it could go to the bottom, lose its sand, and then float back up. Or something like that, I guess.

I dunno... just giving you the idea about densities.

Tie an Alka-Seltzer® tablet to a toothpick with a piece of yarn.

My idea is similar to most of yours. Get a weight with a hook and attach it loosely to some kind of device that will float. When the weight hits the bottom, it should push up enough to detach the device from the hook and it will float up to the top. Like Nate said though, that only works if you're allowed to leave something at the bottom. You said sink and float so I assume motors or propellers of any kind are out.

I know dry ice sinks in water, but CO2 gas is less dense than water. Theoretically if you put enough dry ice in a small closed container to sink it the sublimation process may be quick enough to raise the object to the surface. Just a thought.

Hmm, my sister tried to do this 8 years ago for extra credit in her 6th grade science class. Only one person out of about 200 got it.

I think it had something to do with baking soda and vinegar.

I think there's another way though. You have a container with a hole (or holes) in it. You fill with something more dense than water. It will sink, but then because of the holes, if you drop it in properly, the substance will leak out of the holes and sink to the bottom of the tank of water. Now the container you had should be basically empty. If it is less dense than water, it should float back up to the top.

I don't know though. I'm horrible at science. And I'm only in physics right now. Plus, I skipped chemistry. So yeah. Good luck.

-Westy

search "how to make a submarine" on google.

Tie an Alka-Seltzer® tablet to a toothpick with a piece of yarn.

What the hell's an Alka Seltzer? Sounds scary.

Hmmm, I suck at physics, but these things involving baking soda and tablets sound more technical than 'hooks' so I guess try them out.

Hmmm...you could try and find a material that reacts with water, but only slowly. When you first drop it in it'll sink, but as it slowly reacts, bubbles will attach to its surface, and eventually it'll float back to the top. That's the chemistry-way, anyway, I guess.

Ooh! Or the biology way:

Put a potato chunk in water, and add the enzyme that breaks down the pigment. It forms bubbles on the potato surface and causes it to float. We did it for our practical last year. I didn't do too well though, so maybe you shouldn't take that advice

Alka Seltzer is for getting rid of heart burn and killing sea gulls

here's a site I found on Google. http://pbskids.org/z...marinerace.html
its those ZOOM people but it looks like it will work. COME ON AND ZOOM! COME ON AND ZOOM! COME ON AND ZOOMA ZOOMA ZOOMA ZOOM!

What the hell's an Alka Seltzer?

...

Hmmm...you could try and find a material that reacts with water, but only slowly. When you first drop it in it'll sink, but as it slowly reacts, bubbles will attach to its surface, and eventually it'll float back to the top. That's the chemistry-way, anyway, I guess.

Hehehe, you answered your own question there. Alka-Seltzer are the plop-plop-fizz-fizz tablets taken for heartburn. They famously dissolve quickly in water. One or two would easily sink a toothpick, which would rise again quickly once the bubbles formed by the fizz overcame the steadily diminishing mass of the tablet(s).

Ah ha. So I look stupid now

Well, i'd have to say cBass's way looks to be the best. Or AP's, but only cos it's so obscure it'd have to work.

Ah ha. So I look stupid now

Not at all. In fact, we basically had the same idea. You can't be expected to be familiar with every obscure American product.

I don't know about these methods using Alka Seltzer or Baking Soda. It's a Physics class not a Chemistry class, that can't be what they're looking for. I'd try to think of something else. I'm not saying the Alka-Seltzer won't work, it probably will, but do you honestly think that a couple of tablets and a toothpick is going to get you an A on your Honors Physics project?

I'm not saying the Alka-Seltzer won't work, it probably will, but do you honestly think that a couple of tablets and a toothpick is going to get you an A on your Honors Physics project?

I guess the teacher would need to have a results-oriented appreciation of creatively simple solutions.

I see your point, though. The chemistry is creating the effect, but it's still the physics of boyancy that make it go down and up.

I recall doing this once in class...but we used a variety of different ways, and few worked...

One i recall that worked fairly well, but was kinda complicated to set up correctly...

If you fill a small balloon with sand (or other dense material), have a thin piece of cardboard set up underneath the balloon, with the handle end of a knife pointed down, and the sharp point through the cardboard but not the balloon....

When you drop the balloon, the balloon should drop fast enough to allow the impact of the bottom of the tank and the handle of the knife to puncture the balloon, releasing the sand (or material), and rising the deflated balloon back to the top.

Now, a few things to be aware--- this would be pretty messy, the balloon would be destroyed, and the knife wouldn't return to the top...

oh well.