# NTNUJAVA: Virtual Physics Laboratory: Enjoy the fun of Physics

• How to make gravitational simulation ? by:GwenArBreizhouat 2011/12/24 23:48Hi,
I would like to try the simulator to make a simulation where gravitational forces appears while you can change weight and radius of planets and distance from them.
I found E field and B field simultor but nothing for a G field ...

How can I do ?

best regards,

See 21 replies click

1. Re: How to make gravitational simulation ? by:hwangat 2011/12/25 18:20The following simulation show gravitation field as function of r.
You can change the radius of the planet with the slider.
You can also drag mouse to any position and the simulation will show gravitation field at the new mouse position.
I hope this is what you need!

2. Re: How to make gravitational simulation ? by:GwenArBreizhouat 2011/12/25 21:27Thanks for reply.
This is part of what I would like to do.
I don't need gravitation field but just the force applied on an object which weight and position can be changed.
Also, I would like to be able to change weight of the planet and not only the radius.

Regards,

3. Re: How to make gravitational simulation ? by:hwangat 2011/12/26 00:08The weight of the object depends on gravitation field g and mass of the object m. i.e. weight =m*g

And Usually the mass/size of the object is much smaller than the planet.

[quote]
Also, I would like to be able to change weight of the planet and not only the radius.
[/quote]
Do you mean the mass of the planet instead of weight of the planet?

The mass of the planet is proportional to volume of the planet. $M=\rho\frac{4\pi r^3}{3}$

4. Re: How to make gravitational simulation ? by:GwenArBreizhouat 2011/12/26 00:23[quote author=Fu-Kwun Hwang link=topic=2365.msg8844#msg8844 date=1324829323]
Do you mean the mass of the planet instead of weight of the planet?
[/quote]

Yes of course.
Sorry but each time I used "weight", I meant "mass".

The mass of the planet is proportional to volume of the planet. $M=\rho \frac{4\pi r^3}{3}$
[/quote]

In a way yes. But it depends on density.

5. Re: How to make gravitational simulation ? by:hwangat 2011/12/26 15:23I modified the code: you can change the density,too!
And it will display gravitation field.
If you need the force, just multiple the gravitation field by mass of the object.

6. Re: How to make gravitational simulation ? by:GwenArBreizhouat 2011/12/26 17:23Thanks for these modifications.

It seems to be a problem while if r > 0.6, g don't change anymore.

As the gravitation field is concerned, would it be possible to have it as an option because I work with 15 years old students and it will be difficult for them to understand the meaning of such a field ?

Can we have instead a cursor where m of the object can be changed and the value of force would appears in the simulation ?

best regards,

7. Re: How to make gravitational simulation ? by:hwangat 2011/12/26 20:18The initial value for diameter is D=0.6 (mean r=D/2=0.3).
g=0.42 is gravitation field strength at r=0.3

The gravitation field will not change if you increase the radius of the planet.
(The uniform mass outside radius r will not contribute to gravitation field).

I added an object (blue dot) and user can adjust it's mass with slider.
The gravitation force is shown as black arrow.
User can drag the object with mouse,too!
I hope this version is closer to what you need!
Enjoy it!

8. Re: How to make gravitational simulation ? by:GwenArBreizhouat 2011/12/27 04:45[quote author=Fu-Kwun Hwang link=topic=2365.msg8848#msg8848 date=1324901907]
I hope this version is closer to what you need!
[/quote]

Yes in fact, it is.
To achieve, I would like to know if the gravitational potential could be an option like "g" and if it's possible to put a legend (planet, object, gravitational force, gravitational field) and to let me do a french version of this simulation.

Thanks in advance (I hope it's the last time ;o))

9. Re: How to make gravitational simulation ? by:hwangat 2011/12/27 23:00The simulation has been modified according to your suggestion!

10. Re: How to make gravitational simulation ? by:GwenArBreizhouat 2012/01/31 05:46Hi,
I begin to use your simulation with students (15 years old) without translating it because I don't remember how to do it.
Can you refresh my memory ?

The student are a little surprised with the potential curve. Would it be possible to put it as an option ?

Best regards,

11. Re: How to make gravitational simulation ? by:hwangat 2012/01/31 09:37The simulation has been modified (add an option for[b] show V[/b]:potential curve).

For the translation: Please check out [url=http://www.um.es/fem/Ejs/WebCasts/en/EJSTranslationFacilities/index.html]How to translate a simulation created with EJS[/url]

You are also welcomed to check out Getting started with EJS

12. Re: How to make gravitational simulation ? by:GwenArBreizhouat 2012/01/31 21:29Hi,
I got a problem. When I right-click on the simulation and ask for opening EJS model, I'm told that "Easy Java Simulations are not found" as you can see in the attached file.

I tried as well after putting your users_ntnu_fkh_gravitationfnr.ejs in the directory but I got the same message.

What can I do ?

13. Re: How to make gravitational simulation ? by:ahmedelshfieat 2012/01/31 23:25I believe the applet gonna work if you mark use original path, try do it again, he gonna work with you.

14. Re: How to make gravitational simulation ? by:hwangat 2012/01/31 23:281. You need to install EJS (just unzip the file)
2. run EJSConsole.jar and you need to select working directory when you run it for the first time.
You can select workspace under EJS installed directory.
However, I would suggest you create another directory under root (e.g. c:\workspace).
This would be easier when you install new version later. (because you do not need to change working directory again)

15. Re: How to make gravitational simulation ? by:GwenArBreizhouat 2012/02/01 02:20Hi,
I finally managed to translate the simulation. I therefore attach the version that can get it in French.
Thank you for all that time spent helping me,
Regards,

16. Re: How to make gravitational simulation ? by:hwangat 2012/02/01 16:52I just added another option (a link just below the applet).User can translate strings in simulation to different language format with web interface before download.

However, user need to make sure the character coding for the browser should be set to utf-8 (i.e. unicode).
User will be able to download updated jar file after the translation has been done.
You can try it with the above simulation.

17. Re: How to make gravitational simulation ? by:GwenArBreizhouat 2012/02/13 06:51I've just tried but I obtained an error 404

18. Re: How to make gravitational simulation ? by:hwangat 2012/02/16 16:12I just download it without any problem, please try it again!

19. Re: How to make gravitational simulation ? by:jhon marviat 2012/12/21 13:15Artificial gravity is the varying (increase or decrease) of apparent gravity (g-force) via artificial means, particularly in space, but also on the Earth. It can be practically achieved by the use of some different forces, particularly the centrifugal force and linear acceleration (fictitious forces).

The creation of artificial gravity is considered desirable for long-term space travel or habitation, for ease of mobility, for in-space fluid management, and to avoid the adverse long-term health effects of weightlessness.

20. Re: How to make gravitational simulation ? by:sunnnyat 2015/03/28 15:40Also, each green is given a Stimp Meter reading to indicate the speed of the green.  Stimp Meter is a 36 inch stick with V-shaped grooves.  It will be raised to 20.5 degrees and a golf ball (1.62oz) is placed at the 30 inch mark and released down the grove.  A Stimp Meter of 8 means the ball travels 8 ft (96 in) after it leaves the Stimp Meter.

21. Re: How to make gravitational simulation ? by:lookangat 2015/05/06 13:49dear prof,

the potential requires a negative sign  :D

http://iwant2study.org/lookangejss/02_newtonianmechanics_7gravity/ejss_model_gravity07_1/gravity07_1_Simulation.xhtml