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 by Alfonso Gonzalez

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In order for a buoyant force to be great enough to make an object float, does the object need to be less dense than water? If you think that yes, an object does have to be less dense than water to float, then how does a metal ship float? Explain that. How does a concrete boat float (remember the video we saw.) Please explain your answer by leaving me a comment.

(For those of you not from Chimacum who wish to add an answer or challenge something you read here are some of the resources we used: Density and Buoyancy Links.)

Article posted February 11, 2009 at 09:13 AM • comment (35) • Reads 82 • Return to Blog List

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The object would have to be less dense the the water, otherwise the object would sink. Metal ships can float because they are less dense than the water and it would need to be either the same or less than the weight of however much water it displaces, to allow it to float.
Posted May 1, 2009 at 01:15 PM by • Morgan N
Posted May 1, 2009 at 01:15 PM by • Morgan N
the object would definitely have to be less dense otherwise it would sink.
and a metal ship can float because they are less dense than the enitre ocean.
Posted May 1, 2009 at 01:14 PM by • maureen c
Posted May 1, 2009 at 01:14 PM by • maureen c
Hello,
This is not a comment for posting but I didn't know how else to contact you. Thank you for responding to Stargirl about her insensitive comment to one of your students. I hope you understand why I will not post your comment on her blog, as it is not appropriate there, either. I will , however, share it with her before deleting. Please contact me personally should you find anymore comments like this. This is how many other teachers and I deal with teaching our students how to comment more appropriately. It will also allow us to communicate. Last year, I had to send a similar message to another teacher and we started a blog buddy system with commenting. It was most beneficial. Perhaps, we can do something similar.
Thank you.
Lisa Parisi
South Paris Collaborative
collaborative@herricks.org
Posted April 24, 2009 at 07:42 PM by • Lisa Parisi
Posted April 24, 2009 at 07:42 PM by • Lisa Parisi
yes it has to be less dense then water. for an objectlike a metal or concrete boat to float it needs to weigh the same or less then the amount of the water it displaces
Posted March 18, 2009 at 01:10 PM by • cole
Posted March 18, 2009 at 01:10 PM by • cole
When something is more dense than water, it is negativly buoyant.
Posted March 16, 2009 at 09:24 PM by • erinb
Posted March 16, 2009 at 09:24 PM by • erinb
Yes the item needs to be less dense than water and it also needs to weigh the same or less than the water it displaces and it will float.
Posted March 16, 2009 at 04:49 PM by • Caseys
Posted March 16, 2009 at 04:49 PM by • Caseys
Yes. A metal ship can float cause it displaces enough water to help it float and it also has the air inside to help it float
Posted March 12, 2009 at 01:33 PM by • kaleb l
Posted March 12, 2009 at 01:33 PM by • kaleb l
Yeah, It has to be less dense then water. And a concrete or metal boat floats because its less dense then the water it displaces.
Posted March 11, 2009 at 05:34 PM by • Brittney
Posted March 11, 2009 at 05:34 PM by • Brittney
Yeahhh, i agree.
Thaat most things need to be less dense than water.

because if it were more dence thann the water it would sinkkkkkkkkk.

(:
Posted March 10, 2009 at 06:17 PM by • Kristinnnnnnn L
Posted March 10, 2009 at 06:17 PM by • Kristinnnnnnn L
I agree with you because if an object is more dense than water it will sink
Posted March 10, 2009 at 12:57 PM by • Taylor H
Posted March 10, 2009 at 12:57 PM by • Taylor H
In order for an object to float in water it's density must be less than water. Another way to float like what huge metal ships do is that they displace more water than they weigh. So that's why even concrete boats can float. Most ships use air to make the density of the boat less than water so that's why huge metal ships float but if there's a hole in them then the air is replaced by water and thus, the ship sinks because it becomes more dense than the water. That's why some wooden boats are hard to sink because wood is less dense than water so even if there's a hole in them it's still hard to sink. So metal ships float because they displace more water than they weigh and they're filled with air. Wooden boats float because they are less dense than the water.
Posted March 10, 2009 at 12:31 AM by • Daryl
Posted March 10, 2009 at 12:31 AM by • Daryl
yes...the boat has to be less dense than the water or it would sink of course. the boat also has air inside to help keep it afloat. Check out my blog! i changed it!
Posted March 5, 2009 at 06:40 PM by • CRYSTINA
Posted March 5, 2009 at 06:40 PM by • CRYSTINA
i do agree... because the boat has to be less dence than the water to float. and i think the concrete boat will float because of its shape.
Posted March 5, 2009 at 02:46 PM by • Daciap
Posted March 5, 2009 at 02:46 PM by • Daciap
Hey! I am at home at the moment and I was going through my grades. I think that MaryJanes comment is just a different way of saying that something that floats has to be less dense than the water.
Posted March 4, 2009 at 09:00 PM by • Annap
Posted March 4, 2009 at 09:00 PM by • Annap
The amount of water something displaces determines the buoyancy.
Posted March 4, 2009 at 07:26 PM by • Akash
Posted March 4, 2009 at 07:26 PM by • Akash
oh and yes i do agree!!!
Posted March 3, 2009 at 06:00 PM by • kayleet
Posted March 3, 2009 at 06:00 PM by • kayleet
the boat would need to be less dense than water or it just needs to weigh less or the same weight as the water it displaces
Posted March 3, 2009 at 05:59 PM by • kayleet
Posted March 3, 2009 at 05:59 PM by • kayleet
Ya an object needs to weigh less oror the same as water and a boa has air in it to help it float.
Posted March 3, 2009 at 12:24 AM by • dereka
Posted March 3, 2009 at 12:24 AM by • dereka
Yes the boat does have to be less dence than water. The boat also has to weigh less or the same amount of the space it takes up. For the boat to float the air inside espacially has to help with the density to make it less dense.
Posted February 28, 2009 at 03:13 PM by • abbi
Posted February 28, 2009 at 03:13 PM by • abbi
yes. i do agree that most things need to be less dense than water. But big metal boats i think float because of the its shape
Posted February 27, 2009 at 07:46 PM by • dacia p
Posted February 27, 2009 at 07:46 PM by • dacia p
I think that metal boats can float partly because of the shape of the bottom, partly because air inside the boat helps it float, and that the constant forward motion helps keep it afloat.
Posted February 26, 2009 at 08:07 PM by • Jonathan
Posted February 26, 2009 at 08:07 PM by • Jonathan
Yes. A metal ship can float cause it dislaces enough water to help it float and it also has air inside to help it float.
Posted February 25, 2009 at 07:04 PM by • seth h
Posted February 25, 2009 at 07:04 PM by • seth h
No beacause if it has more air in it i think it would steel float.
Posted February 24, 2009 at 11:36 PM by • tihune
Posted February 24, 2009 at 11:36 PM by • tihune
for something to float in water, the object needs to weigh less or the same as the amount of water it displaces.
Posted February 24, 2009 at 11:09 PM by • olivia G :]
Posted February 24, 2009 at 11:09 PM by • olivia G :]
Yes the object needs to be less dense than water and it also needs to weigh less or more than the water it can displace.
Posted February 24, 2009 at 05:26 PM by • kaleibr
Posted February 24, 2009 at 05:26 PM by • kaleibr
no, a dense object can float with air.
Posted February 22, 2009 at 04:31 PM by • mikyas
Posted February 22, 2009 at 04:31 PM by • mikyas
I agree with the things that it says it has to be less dense then water and Maryjanes works to it does displace water to make either float or sink if the object is heavier them 1g/cm3 them it will sink if it is around 1g/cm3 then it will suspend and if its lighter then 1g/cm3 it will float! so i agree!!!!
Posted February 21, 2009 at 09:50 AM by • Malloric
Posted February 21, 2009 at 09:50 AM by • Malloric
i agree that things need to be less dense than water to keep afloat but the big tanker have other buoyant forces like air witch makes them less dense than water and me
Posted February 19, 2009 at 11:26 AM by • ericr
Posted February 19, 2009 at 11:26 AM by • ericr
I disagree with all the other comments, and no, something does NOT need to be less dense than water to float, it just needs to weigh less or the same weight as the water it displaces. Soooo... check out my blog please! THANK YOU!
Posted February 19, 2009 at 11:19 AM by • MaryJane R
Posted February 19, 2009 at 11:19 AM by • MaryJane R
I do agree that most thing need to be less dense that water to float, but a big steel boats have something els to keep them a float . A big steel ship, with its outwardly curved sides pushes aside, or displaces a great deal of water, Enough to float the ship.
Posted February 18, 2009 at 02:09 PM by • nathan
Posted February 18, 2009 at 02:09 PM by • nathan
I do agree with your answer because if an object in water was more dense than the water it was in it would sink .
Posted February 18, 2009 at 11:05 AM by • Krista
Posted February 18, 2009 at 11:05 AM by • Krista

You are all agreeing that the object floating needs to be less dense than water to float. So then how do items made of dense metal float? How do ships float? How does a boat made out of concrete float?
Posted February 17, 2009 at 11:55 PM by • Mr. G
Posted February 17, 2009 at 11:55 PM by • Mr. G
The object would need to be less denser than water to float. but if the object is more dense than the water it would sink to the bottom. :) See ya check out my blog.
Posted February 17, 2009 at 07:26 PM by • haileej
Posted February 17, 2009 at 07:26 PM by • haileej
Yes, because if the object were more dense than the water it wouldnt float. But since its less dense it will.
Posted February 17, 2009 at 02:05 PM by • Justice
Posted February 17, 2009 at 02:05 PM by • Justice
The object needs to be less dense than the water because if it were more dense it would sink.

=]
Posted February 17, 2009 at 02:03 PM by • Cydney
Posted February 17, 2009 at 02:03 PM by • Cydney

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I started my teaching career in South Central Los Angeles teaching in modified to full bilingual 4th and 5th grade classes. Then I moved to WA State where I have taught mainly 6th through 8th grade. I have enjoyed the culture clash but notice that kids are the same everywhere :o)

My areas of interest are science and technology but I also love studying ancient cultures and learning about different peoples and cultures.

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