Buoyant Force

[Fu-Kwun Hwang]

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There are 1 translations, select to view translated versionΕλληνικά - Greek(by abascare: 129)
Higher number at the end means more translation been done.

or

A completely submerged body displaces a volume of liquid equal to itsown volume. Experience also tell us that when an object is submerged, itappear lighter in weight; the water buoys it up, pushed upward, partiallysupporting it somehow. Archimedes' Buoyancy Principle asserts that

an object immersed in a liquid will be lighter by an amountequal to the weight of the fluid it displaces.

The upward force exerted by the fluid is known as buoyant force.

Buoyant force is caused by gravity acting on the fluid. It has its originin the pressure difference occurring between the top and bottom of theimmersed object, a difference that always exists when pressure varies withdepth. Imaging without the object, the same immersed space will be occupiedby the same volume of fluid.
The weight of those fluid is supported by other parts of the fluid.So the buoyant force is the weight of the displaced fluid. I hope thisjava applet will help you learn more about buoyancy.

The java applet is divided into two area.
The cyan region represents the fluid . The gray block is the object.
You can enter values into the text field to changethe density of the fluid or the object.

There is a drag force Fr when the object is moving in the fluid.
    Fr = - k v where v is the object'svelocity.
k is the propotional coefficient (the 2nd text field)

Click the LEFT mouse button in gray block and drag the objectto some other place.
    Numbers shown in the upper left pairs are the Xcoordinate and the width of the object.
    Number shown in the upper right pairs are the Ycoordinate and the height of the object.
Click the RIGHT mouse button in gray block and drag the mouse
    to change the volumeof the object.
The mass of the object is shown in the textfield.

You can drag the object and let it submerged in the fluid.
    Black vector represents  the weightof the object. Black circle is the center of gravity.
    Red vector represent the buoyantforce.
    RIGHT CLICK the mouse button near the origin(green circle)
        to clear the curves andreset time to zero t=0.0s.
    The buoyant force can be treated as acting at thecircle in cyan
        (same as the center of gravityfor the displaced liquid).

The animation starts when you release the object.
    (Gravitation force and buoyant force trigging themotion of the object)
Blue curve is the displacement in y-directionof the object verses time.
Red curve shows the velocity of the objectas a function of time.

Click the Pause button to hold the animation, RIGHT CLICK mousebutton to resume.

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
If java program did not show up, please download and install latest Java RUN TIME

There are 1 translations, select to view translated versionΕλληνικά - Greek(by abascare: 129)
Higher number at the end means more translation been done.

or

[yepengsong]

I feel that it would be better to use Newton to measure the forces acting on the object in your animation.

[Fu-Kwun Hwang]

Yes. The unit can be shown in Newton (N). Then 10kgw will be equal to 98N.
The unit for the density is g/cm³

[abascare]

Dear Fu-Kwun, when the "buoyant force" sim is translated into Greek the data is saved in Chinese characters.
the URL you asked is below. My user name is abascare.

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=266.msg1251#msg1251.

Can you help please?
thank's a lot

Nikos

[Fu-Kwun Hwang]

Could you check out the attached image and find out is it the correct translation for your language.
You need to change character coding for your browser to ISO-8859-1 to view the above page. Otherwise, you will see strange characters (Those are not Chinese characters, either).

The default coding for our system is UTF-8. It seems that your browser was set to ISO-8859-1 as default coding. So the data was stored as ISO-8859-1  character set.

I will try to find out a way to detect user's character coding.

[abascare]

thank you, I will try it.

[Fu-Kwun Hwang]

Could you let me know if the characters shown in the above image are correct or not?
If they were not correct, then, it might be due to other problem.
I need your confirmation because I can not recognize those characters.

[abascare]

No, they are not correct.
Thank's a lot for your help and for your efforts.

[Fu-Kwun Hwang]

Is it possible for you to give me a snapshot image which show correct characters?
A snapshot of the web page which you were doing the translation (before and after  you submit) will be  very helpful for me to find out the problem.

[abascare]

following is a translation in my local language of your text in English which is as below:
"A completely submerged body displaces .........................partially supporting it somehow. "

the translated text is like that:
 "Ένα σώμα που είναι εντελώς βυθισμένο εκτοπίζει όγκο υγρού όσο ο όγκος του, Επίσης η εμπειρία μας λέει ότι όταν ένα σώμα είναι βυθισμένο, δείχνει να είναι ελαφρότερο, το νερό το σηκώνει προς τα πάνω, κατά κάποιο τρόπο υποστηρίζοντας το."
After I submit it, I see someting like:
"鍚╫?/h2>
貲?嚲憼 豵?橀罅?樇醲錌?碬鴇鶂楜?樏鐐謵緪?膬 礯厴???膬?鐐? 黴裍趛 ?樦謥濄葐 憼?錧樥 ?摿 楜?嚲憼 橀
hope I have helped you.

[Fu-Kwun Hwang]

Please check out the attached image.
You need to select "ISO-8859-7" to be able to view it like the one in the attached image file.
I believe it is the correct one. And the java applet also shown correctly.

It is due to your browser was set to "ISO-8859-7" when you did the translation.
So characters are stored as "ISO-8859-7".
Add the following line to the html page when you unzip the download file.

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-7" />

add the above line after <html>
And it will tell browser to switch to ISO-8859-7 when it load the page.

[lamoonia]

Dear Fu-Kwun Hwang,

I liked this simulation very much. I was searching the web for such a simulation but couldn't find one, not even commercial simulators have these features.

So at first, let me thank you for your great work. Maybe USA is right in fearing China 

I have two main interests at this time regarding this simulation called Buoyant Force.

1. I want to simulate the effect of a free falling body and how its speed changes swiftly as it hits the water surface. This is to show the power of water buoyancy and its effect on gravity (as anti-gravity force.)
2. I want to simulate the effect of high water pressure of deep sea. I want to submerge a container (after entering its properties) and see when this container gets imploded by sheer water pressure.
3. I want to simulate the effect of water buoyancy on free fall. I'm especially interested in showing how fluid properties (density, salinity, temperature) and gravitational constant (g) affect free fall's terminal velocity. I need this to simulate probes sent to outer space esp. Venus (atmosphere 90 times thicker than earth), Mars (gravity constant half of earth) and Jupiter (gravity 13 times but size 100 times and atmosphere - I think - nearly as thick as water.)

To achieve these interests, your simulation will need these extra features:

a. Ability to record the simulation data whether as a graph or output file.
b. Ability to load an image or vector graphic in place of the solid brick. This is to make simulation feel closer to real world.
c. Ability to change gravitational constant (g).
d. Ability to change salinity of water.
e. Ability to change water temperature.
f. Ability to specify properties of atmosphere.
g. Larger screen size.

I hope the above information is sufficient to build/modify the applet.

Thank you for your reply, Aamir Berni.

[Fu-Kwun Hwang]

1. I want to simulate the effect of a free falling body and how its speed changes swiftly as it hits the water surface. This is to show the power of water buoyancy and its effect on gravity (as anti-gravity force.)

Do you need to consider the drag force or just consider the bulyant force?

2. I want to simulate the effect of high water pressure of deep sea. I want to submerge a container (after entering its properties) and see when this container gets imploded by sheer water pressure.

How depth/ how high is the pressure range? Need data of water density as function of depth.

3. I want to simulate the effect of water buoyancy on free fall. I'm especially interested in showing how fluid properties (density, salinity, temperature) and gravitational constant (g) affect free fall's terminal velocity. I need this to simulate probes sent to outer space esp. Venus (atmosphere 90 times thicker than earth), Mars (gravity constant half of earth) and Jupiter (gravity 13 times but size 100 times and atmosphere - I think - nearly as thick as water.)

Need density of water as function of salinity and pressure.
It is better if you can provide a physics model with proper parameter values.

a. Ability to record the simulation data whether as a graph or output file.

It can be done with EJS. However, I need to know what kind of data need to be drawn/saved.

b. Ability to load an image or vector graphic in place of the solid brick. This is to make simulation feel closer to real world.

Please provide image file (gif/jpeg or png)

c. Ability to change gravitational constant (g).

It is basics feature. Let me know the range you want to be adjusted.

d. Ability to change salinity of water.
e. Ability to change water temperature.

Need model related to salinity of water and temperature(e.g. density as function of salinity or temperature.)

I can created the simulation if I have full physics model (with proper parameters).

f. Ability to specify properties of atmosphere.

What dose this mean? What need to be changed?

g. Larger screen size.

What is the screen size you need!

[abascare]

thank's a lot for your help
Nikos