Monday, December 30, 2013

EJSS Earth and Moon Model

EJSS Earth and Moon Model by paco remixed by lookang.


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} $


$\ 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

changes made:

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


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?

Sunday, December 29, 2013

EJS 5.0 simulations recompiled

enjoy! download all 91 simulations through the dropbox links on caption of each picture!

  1. MEASUREMENT Physical Quantities: Time pendulum

      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
      author: Wolfgang Christian and F. Esquembre and lookang
  2. MEASUREMENT Physical Quantities: Time Pendulum for Primary School
    Primary School remix for Pendulum by
    Author: Wolfgang Christian and F. Esquembre
    Author: lookang (remix version)
    Author: W. Christian, F. Esquembre , lookang and (this primary school version)

  3. MEASUREMENT Physical Quantities: 15 Pendulum uncoupled for amazing wave effect Open Source Fifteen uncoupled simple pendulums model
    Author: lookang based on the works of

  4. MEASUREMENT Physical Quantities: Stop Watch

    Ejs Open Source Stop Watch Model Java Applet with enhanced integer values for game and minute/second hands
    author: dhasthagheer, added on by Fu-Kwun Hwang, and now slightly remixed by lookang

  5. MEASUREMENT Physical Quantities: Stop Watch 2

    Ejs Open Source Stop Watch and Timer Model Java Applet with enhanced integer values for game and minute/second hands
    author: dhasthagheer, added on by Fu-Kwun Hwang, and now slightly remixed by 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
    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!
    Author: Fu-Kwun and lookang (this remix version)
  8. MEASUREMENT Physical Quantities: Vernier Callipers

    31 October 2011 added magnify and random length objects to challenge students to think more, hopefully more fun to figure out for themselves!
    author: Fu-Kwun and lookang (this remix version)

  9. MEASUREMENT Physical Quantities: Micrometer

    added ability to magnify and a randomize object width
    authors: Fu-Kwun and lookang and wolfgang
  10. Scalars and Vectors: Represent vector of horizontal and vertical components
    Author: lookang and Fu-Kwun

  11. Scalars and Vectors: Magnitude of a Vector
    Author: lookang

  12. Scalars and Vectors: Resolving a Vector in 2 Perpendicular Directions
    Author: Fu-Kwun and lookang

  13. Scalars and Vectors: Vector Addition by Graphical Method
    Author: Fu-Kwun and lookang

  14. Newtonian Mechanics: Ticker Tape Timer

    7. Ticker Tape Timer
    author: engrg1

  15. Newtonian Mechanics: Kinematics of 1 object Horizontally
    Author: Fu-Kwun and lookang

  16. Newtonian Mechanics: Kinematics of 1 object Horizontally (Phet the moving man)

    The Moving Man
    click to run PheT appet

    (abandon attempt) Ejs Open Source Position, velocity, and acceleration graphs
    author: lookang

  17. Newtonian Mechanics: Kinematics of a Car, Traffic Light and Reaction Time
    Ejs Open Source Reaction Time Measurement Traffic Light Model Java Applet
    authors:Fu-Kwun Hwang this version remixed by lookang

  18. Newtonian Mechanics: Projectile Motion With and Without Air Resistance
    Projectile Motion (with/without air resistance)
    author: lookang based on the works of paco
    worksheet by
    RVHS (lead):

  19. Newtonian Mechanics: Rectilinear Motion of 2 Objects Racing
    author: fu kwun and lookang

  20. Newtonian Mechanics: 2D Elastic Collision
    author:Fu-Kwun Hwang, edited by Wolfgang Christian and Robert Mohr very slightly edited by lookang

  21. Dynamics: Newton's Laws of Motion 1st Law
    author: woflgang and lookang

  22. Dynamics: Newton's Laws of Motion 2nd Law

    Open Source Rocket Physics Java Applet Model by lookang, based on assignment given by Larry Engelhardt
    author: Larry Engelhardt and assignment completed by lookang 

  23. Dynamics: Modified Atwood Machine by Tat Leong

    Ejs Open Source Modified Atwood Machine Model Java Applet
    author: Lee Tat Leong ,remixed by lookang

  24. Dynamics: Rolling Down a Slope

    a car rolling down a slope and colliding with bumper with coefficient of restitution e = 0.2
    author:Ejs Open Source Rocket Car on an Inclined Plane Java Applet is by Wolfgang Christian, Francisco Esquembre, and Mario Belloni using the Easy Java Simulations (Ejs) modeling tool, now remixed by lookang

  25. Dynamics: Block Moving on a Horizontal Plane with Friction

    Ejs Open Source Frictional Mass Block moving on Horizontal Plane Java Applet by Fu-Kwun Hwang, remixed by lookang
    author:Fu-Kwun Hwang, remixed by lookang

  26. Dynamics: 1 Direction Collision Force Model
    collision cart
    author: lookang, paco and engrg1
    worksheets by

  27. Dynamics: Sphere Rolling Without Slipping
    Ejs Open Source Rolling Solid & Hollow Sphere with Slipping java applet
    author: Hwang Fu Kwun and lookang

  28. Energy: Energy Conversion and Conservation of a Roller Coaster

    15 june 2011 version with a circular loop, have not implemented the drag coefficient k yet. :)
    author: mike gallis, remixed by lookang

  29. Energy: Kinematics of Uniform Circular Motion
    Ejs Open Source Uniform Circular Motion Derivation of a = v^2
    author: fu-kwun hwang and lookang

  30. Gravitational Field: How to Measure Radius of Earth by Eratosthenes

    Ejs Open Source Eratosthenes Measures Earth Java Applet by Todd Timberlake, remixed by lookang, version public domain earth from Tom Patterson, Thanks Todd and Tom!
    author: timberlake and lookang

  31. Gravitational Field: Kepler's 3rd Law (T^2/r^3=constant)

    version 20August 2013.
    older version:
    author: timberlake and lookang
    worksheets by (lead) YJC: same link of four simulations
    scaling IJC:

  32. Gravitational Field: Field near to the Earth
    Ejs Open Source Gravity Field Model Near Earth Java Applet
    author: lookang based on the works of fu-kwun hwang

  33. Gravitational Field: Gravitational Potential 1 Dimension
    added g proportional to r inside sphere of constant density as suggested by tatleong. re-implemented dotted lines of g1 g2 and phi1 and phi2 with no lag after using the group to contain them.
    author: lookang and andrew based on andrew duffy early model
    worksheets by (lead) YJC: same link of four simulations
    scaling IJC:

  34. Gravitational Field: Gravitational potential 1 Dimension Earth & Moon Real Data

    version April 30 2013
    picture of computer model of Earth and Moon gravity system,
    added white background option for printing on lecture notes, fixed bug of g2 showing, latex for g and phi,menu for Earth Moon configuration instead of just Moon Earth previously
    author: lookang and andrew based on andrew duffy early model
    worksheets by (lead) YJC: same link of four simulations
    scaling IJC:

  35. Gravitational Field: Gravitational Field Vector, Field Lines, Potential in 2 Dimensions

    Ejs Open Source 2 Mass Model with Gravity Field Vector, Field Lines, Potential updated 06 sept 2011 with potential and field strength values
    author: fu-kwun hwang and lookang

  36. Gravitational Field: Gravitational Earth Projectile Orbit Newton's Mountain 

    added ability to fire to add velocity to a achieve eclipse orbit and select circular to achieve circular orbit by applying impulse in directions to get velocity at the correct speed and direction, perpendicular to radius. this feature helps in the learning of energies change as satellite move from one circular orbit to another circular as requested by soo kok.
    author: timberlake, lookang and fu-kwun hwang 

  37. SHM & Circular motionResonance
    Ejs open source java applet Resonance simple harmonic motion SHM
    author: lookang based on the works of prof paco

  38. Thermal Physics: Particle model for solid liquid gas states
    Particle model for solid liquid gas states by Fu-Kwun Hwang

    author: Fu-Kwun Hwang and lookang

  39. Thermal Physics: Heat capacity and Specific heat capacity of cylinder block 

    screenshot of Ejs Open Source Heat capacity and Specific heat capacity Java Applet by lookang, customized based on an earlier model
    author: Wolfgang Christian and lookang.

  40. Waves: General Wave Properties & Representations
    Ejs Open Source Wave Representations Model Java Applet Simulation

  41. Waves: Progressive waves & Superposition
    added (1) autoscale x axis false, (2) -T/8 button (3) blue color for wave 2 for greater contrast on the projector screen thanks to joshua yeo.
    author: wolfgang and lookang

  42. Waves: 3D Wave Machine 
    author: Wolfgang Christian, this remixed version is by lookang,

  43. Waves: Sound wave travel at v = 330 m/s application at fireworks
    Ejs Open Source Sound Travel FireWorks Model
    author: fu-kwun hwang and lookang

  44. Waves: Doppler Effect sound Wave
    Ejs Open Source 1 Dimension Doppler Effect Sound Wave Java Applet with features like f = \left( \frac{c \pm v_r}{c \mp v_{s}} \right) f_0 \,, counters for waves emitted and detected
    author: lookang based on the works on Fu-Kwun Hwang, Juan M. Aguirregabiria and Andrew Duffy

  45. Waves: Light and Shadow Model
    Light and Shadow Model with trick question.
    1 light source through a slit ( or 2 pink blocks) , notice the shadow-umbra and the light-bright light.
    author andrew duffy, remixed by lookang

  46. Waves: Refraction of Light
    author fu-kwun hwang, remixed by lookang

  47. Waves: Light and Lens Intensity Drops when Block
    Ejs Open Source Lens with light path block to show intensity drops shows intensity drops instead of part of the object is missing, a misconception that is probably partly due to the teaching of principal rays diagrams.
    author: fu-kwun kwang and remixed by lookang

  48. Waves: Thin lenses Light Lens
    bug fixed in convex len light travels in correct direction when image is virtual thanks to
    author: lookang based on the works of fu-kwun hwang

  49. Waves: Electromagnetic wave
    Ejs Open Source Propagation of Electromagnetic Wave Model Java Applet updated with wavelength showing, different implementation axes possible, side view etc
    author: fu-kwun hwang and lookang

  50. Waves: Stationary waves in a pipe
    author: Juan Aguirregabiria and lookang (this remix version)
    Key features designed:
    1. Symbolic text to support visuals NAN, node, anti node node etc.
    2. Can simulate closed or open end of a pipe
    3. Microscopic visual of molecules enhanced with order and random position referencing tat leong code
    4. dt for slowing and speed up simulation 
    5. amplitudes for envelope of displacement visuals
    6. pressures for learning of real equipment sound detector to be placed at the maximum/minimum pressure from the ambient atmospheric as highlighted by kian wee
    7. inputs field for calculation of any length of pipe
    8. modelling-mathematical features as highlighted by peng poo and oon how as key to deepening learning

  51. Waves: Interference
    Ripple Tank Model (Wee, Duffy, Aguirregabiria, Hwang & Lee, 2012) with simplified physics equations modeled, realistic 2D and 3D (shown) visualizations, hints and scientific measurement tools for inquiry activities and data gathering for inquiry learning

  52. Waves: Diffraction grating
    Red Laser: Young Double and Multi Slits Java Applet Ejs Open Source Physics Computer Model
    author: Fu-Kwun Hwang, Robert Mohr, Wolfgang Christian and lookang, took some ideas from andrew duffy laser diffraction main view and tat leong point P,
    many thanks to fu-kwun hwang for teaching me so many things on NTNU java forum

    Blue Laser: Young Double Slit Java Applet Ejs Open Source Physics Computer Model
    author: andrew duffy and lookang, took some ideas from tat leong point P, Jose Ignacio Fernández Palop vcolor
    original work here
    many thanks to fu-kwun hwang for teaching me so many things on NTNU java forum

  53.  Electricity and Magnetism: Force between point charges
    Coulomb Force Model
    author: Anne Cox, Francisco Esquembre, Wolfgang Christian and lookang (this version)

  54. Electricity and Magnetism: Electric field of a point charge
    Ejs Open Source Electric Field & Potential of 2 Charged Particles Java Applet
    author: andrew duffy and lookang 

  55. Electricity and Magnetism: Electric field lines, vectors, potential of 2 point charge
    version 26feb 2013 electric field lines drawn when Q1=-1C, Q2 = 2C
    original authors: Fu-Kwun Hwang and lookang and szeyee
    worksheet by:

  56. Electricity and Magnetism: Magnetic Force on current-carrying conductor

  57. Electricity and Magnetism: Magnetic fields due to currents ( DC Motor )
     Ejs Open Source Direct Current Electrical Motor Model Java Applet ( DC Motor ) « on: October 23, 2009, 06:14:56 PM » posted from:Singapore,,Singapore  author: fu-kwun hwang and lookang

  58. Electricity and Magnetism: Electromagnetic Induction ( AC Generator )
    Ejs Open Source Alternating Current Generator Model Java Applet ( AC Generator )
    author: fu-kwun hwang and lookang

  59. Electricity and Magnetism:  Electromagnetic Induction ( Falling Long Magnet through a Soleniod with AJC and RVHS )
    falling magnet through coil simulation.
    author: paco, lookang,and engrg1
    worksheets by (lead) AJC:

    OPTION added as request by HCI: bar magnet oscillating inside a solenoid java applet
    falling magnet through coil simulation.
    author: paco, lookang,and engrg1
    worksheets by (lead) AJC:

  60. Quantum Theory of Light: Blackbody radiation
    Ejs Open source java applet Blackbody Radiation Spectrum Model for nm remixed by lookang from Fu-Kwun original and some codes adapted from lookang with some codes from Jose Ignacio Fernández Palop
    author: fu-kwun hwang lookang and Jose Ignacio Fernández Palop

  61. Matter Waves: Wave-particle duality
    Double Slit Wave-Particle Duality Model Open Source Physics Java Applet Wolfgang Christian
    notice the interference pattern suggesting wave like property in photon or electron
    when flux =1, the same pattern can be observed, suggesting that photon or electron interferes with itself as it passes through the aperture. Quantum Weirdness simulated by Prof Wolfgang!
    author: Wolfgang Christian and lookang, took some ideas from andrew duffy laser diffraction
    original work here
    many thanks to fu-kwun hwang for teaching me so many things on NTNU java forum

  62. PRIMARY SCIENCE: Cycles Moon Phases
    version 03 Jan 2011
    author: todd timberlake and lookang
    Ejs Open Source Moon Phases Java Applet

  63. PRIMARY SCIENCE: Pendulum Model
    4. Pendulum Model
    author: by Wolfgang Christian Idea

  64. PRIMARY SCIENCE: Spring 
    5, Spring
    author: engrg1
    For teaching of Graphing Skill .

    1. Roller Coaster
    By authors: Michael R. Gallis and edited by Wolfgang remixed by engrg1
    Lesson Idea

  66. PRIMARY SCIENCE: Cooling/Heating Simulation

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