## EJSS Earth and Moon Model by paco remixed by lookang.

 http://weelookang.blogspot.sg/2013/12/ejss-earth-and-moon-model.html https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_model_EarthAndMoon3Dwee/EarthAndMoon3Dwee_Simulation.html source: https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_src_EarthAndMoon3Dwee.zip
 http://weelookang.blogspot.sg/2013/12/ejss-earth-and-moon-model.html https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_model_EarthAndMoon3Dwee/EarthAndMoon3Dwee_Simulation.html source: https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_src_EarthAndMoon3Dwee.zip
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_model_EarthAndMoon3Dwee/EarthAndMoon3Dwee_Simulation.html

## Description:

The Moon completes its orbit around the Earth in approximately 27.32 days (a sidereal month). In this model, we assume the Moon to orbit about the center of the Earth. By this assumption, the Moon is at a distance of about 385000 km from the center of the Earth, which corresponds to about 60 Earth radii. With a mean orbital velocity of 1.023 km/s,[1] The Moon orbit is modeled to be a perfect circular motion orbit, a close approximation the real Moon's orbit. The model also assume the Moon to move on the Earth's equatorial plane.

## The equations of motion are:

$\frac{\delta x}{\delta t} = v_{x}$

$\frac{\delta y}{\delta t} = v_{y}$

$\frac{\delta z}{\delta t} = v_{z}$

$\frac{\delta v_{x}}{\delta t} = - \frac {GMx}{(x^{2}+y^{2}+z^{2})^{1.5}}$

$\frac{\delta v_{y}}{\delta t} = - \frac {GMy}{(x^{2}+y^{2}+z^{2})^{1.5}}$

$\frac{\delta v_{z}}{\delta t} = - \frac {GMz}{(x^{2}+y^{2}+z^{2})^{1.5}}$

## The equations of rotation are:

$\ rotation{earth} = rotation_{earth}+\frac {1}{\delta t}$

$\ rotation{moon} = rotation_{moon}+\frac {1}{360 \delta t}$

## Equations used to calculate physics quantities are:

$\ r = \sqrt{x^{2}+y^{2}+z^{2}}$

$\ v = \sqrt{v_{x}^{2}+v_{y}^{2}+v_{z}^{2}}$

$\ theta = tan^{-1} \frac {y}{x}$

The model used $\delta t = 1$, the time taken for Earth to rotate i complete revolution is therefore
$\ t_{day} = \frac{t}{360}$

so after 360 $\delta t$ steps,
$\ t_{day} = 1$

To calculate period T,

$\ omega = \frac {v}{r}$

therefore,

$\ T = \frac {2 \pi}{\omega}$

For collision detection, i used

$\ r < r_{Earth}+r_{Moon}$

For largely visualization purposes,
$r_{Earth} = 0.637$ some what familiar to real data

$r_{Moon} = 0.1737$ not to scale

in order to create realistic simulation, the model used constants to create numeric that corresponds to the real world.

for example in the model versus in the world,
$M_{Earth} = 0.6 = 6 x10^{24} kg$

$G = 0.667 k = 6.67 x10^{-11} m^{3} kg^{-1} s^{-2}$

where $k = 0.58x10^{-4}$ to achieve comparable period $T = 27.3$ days

$r = 3.844 = 385 000 km$
and velocity of moon is

$v_{cal} = \frac {(v)(1x10^{9})}{k1}$ where $k_{1} = 2.4$ arbitrarily determined

added realistic numbers in the model
added better graphics from creative commons or public domain pictures
added plane of Moon's rotational plane
added control and sliders to suit my usual design ideas

## Activities:

set the velocity to zero and play the simulation, is it as you expected it to observe? What is the physics concepts that can be used to explain this?

1. ## MEASUREMENT Physical Quantities: Time pendulum

 version Ejs Open Source Real Pendulum Model java applet with updated features like theory period, force diagram, energy bars, drag model, reference potential energy, number of complete oscillation counter etc http://weelookang.blogspot.com/2010/06/physical-quantities-and-units.html https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_Pendulumwee.jar https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_Pendulumwee.jar author: Wolfgang Christian and F. Esquembre and lookang

6. ## MEASUREMENT Physical Quantities: Clock 12 hour & 24 hour

 Ejs Open Source Real Clock Model Java Applet by Fu-Kwun Hwang remixed by lookang http://weelookang.blogspot.sg/2011/08/ejs-open-source-real-clock-model-java.html https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_clock24wee01.jar https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_clock24wee01.jar author: Fu-Kwun Hwang remixed by lookang
7. ## MEASUREMENT Physical Quantities: Cathode Ray Oscilloscope

 Ejs Open Source Cathode Ray Oscilloscope CRO Java Applet remixed version and bug fixed! http://weelookang.blogspot.sg/2012/10/ejs-open-source-cathode-ray.html https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_oscilloscopewee.jar https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_oscilloscopewee.jar Author: Fu-Kwun and lookang (this remix version)

9. ## MEASUREMENT Physical Quantities: Micrometer

 added ability to magnify and a randomize object width http://weelookang.blogspot.sg/2010/06/ejs-open-source-micrometer-java-applet.html https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_Micrometer02.jar https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_Micrometer02.jar authors: Fu-Kwun and lookang and wolfgang

92. ## PRIMARY SCIENCE: Cooling/Heating Simulation

author: Wolfgang Christian remixed by engrg1
For teaching of Graphing Skill .