Saturday, June 26, 2010

Ejs Open Source Multi Objects rolling down on an Inclined Plane Java Applet « on: June 18, 2010, » posted from:Singapore,,Singapore

 a car rolling down a slope and colliding with bumper with coefficient of restitution e = 0.2 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
a car rolling down a slope and colliding with bumper with coefficient of restitution e = 0.2

Ejs Open Source Multi Objects (Car,Ball,Shell,Disc) rolling down inclined plane
Ejs Open Source Multi Objects rolling down on an Inclined Plane Java Applet
« on: June 18, 2010,  posted from:Singapore,,Singapore http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1840.0

new repurposed name
Ejs Open Source Multi Objects ( Car , Ball , Shell , Disc ) rolling down on an Inclined Plane Java Applet
i must thanks the man, Fu-Kwun Hwang for his worthy of noble prize forum for informal learning cum community of practice CoP.

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 for learning purposes.
Information about Ejs is available at:
http://www.um.es/fem/Ejs/
and also from the OSP Collection on the ComPADRE Web site:
Access Rights:
Free access
This material is released under the GNU General Public License Version 1.

My thoughts:
so after i am done remixing it, i will also release it's remixed it's source code back, there by guarantee your freedom to share and change free software--to make sure the software is "free to change" for all its users.

ball and ramp for Secondary 1 Science- Physics Average Speed

Objective: Studying the overall speed in a journey

Materials:
x 1 Metal ball
x 4 Electronic stop watches
x Metre-Rule
x Use the ramp to make the track inclined

1. Set the track inclined as shown in the diagram below. Let the ball roll along the track.

Describe the motion of the ball on the track.

Is motion constant speed?

Measure and record the time taken for the ball to travel from the start point to the 30cm,
60cm, 90cm and 120cm markings. Adjust the inclination if necessary so that you can
measure the time comfortably.

Calculate the average speed of the ball from Start point to 120cm.

Set the track inclined as shown in the diagram below. Let the ball roll along the track.
1. In your team, choose one of your team members to place a finger at the 60cm mark to stop the
rolling ball.
2. After stopping the ball for few seconds, remove the finger and let the ball to continue rolling
along the track.
3. Measure and record below the total time taken for the ball to travel from the start point to
120cm mark.

What is the average speed of the ball when it travels from the start point to 120cm mark?

original activity:
This simulation uses Easy Java Simulations (Ejs) to model the problem of a rocket car on an incline plane. When the car reaches the bottom of the incline it can be set to bounce (elastic collision) with the stop attached to the bottom of the incline. The total mass of the car is 2.0 kg which consists of the car body (1 kg), two front wheels (0.4 kg) and two rear wheels (0.6 kg). The front and rear wheels rotate and are uniform disks. In the simulation you can set the incline angle (in radians), the bounce, the thrust of the car's rocket (in Newtons), and you can drag the car to its initial position.

Questions

1. Calculate the change in potential energy of the car when it reaches the bottom of the incline. Your answer should be given in terms of the mass of the car body mB, the mass of the front and rear wheels, mF and mR, the incline angle θ, and the distance the car moves down the incline, L.
2. Calculate the velocity of the car at the bottom of the incline when subject to an arbitrary thrust, T, from its rocket. Don't forget that the wheels of the car rotate. Your answer should be given in terms of the variables described in Question 1 and the thrust, T. Once you have a general form for the velocity, check your answer against the simulation.
3. Given the velocity you found in Question 2, determine the acceleration of the car subject to an arbitrary thrust, T. Again your answer should be given in terms of the variables described in Question 1. Once you have a general form for the acceleration, check your answer against the simulation. Also find the thrust that yields zero acceleration of the rocket.
4. Calculate the velocity of the car at the bottom of the incline when subject to an arbitrary thrust, T, from its rocket. Your answer should be given in terms of the variables described in Question 1 and the thrust, T and the distance the car moves down the incline, L. Once you have a general form for the velocity, check your answer against the simulation.

Wednesday, June 23, 2010

SC883 Interaction & Discourse in Education Research

http://teachers.nie.edu.sg/portal/page/portal/TeacherPortal/ContentDetails?paramMainTab=132¶mNodes=580

1 Course Code SC883
2 Course Title Interaction & Discourse in Education Research
4 Medium of Instruction English
5 Lecturer / Coordinator¶V
name, telephone no. &
e-mail
Lee Yew Jin; 67903848; yewjin.lee@nie.edu.sg
6 Assessment Mode Four written assignments spread throughout the course
8a For classes meeting
regularly over approx 13
weeks

Time of Day
Day of Week
Date of First class

1800 ± 2100 hr
Mondays
6 Sep 2010
8b Alternative Schedule -
9 Venue NIE
10 Maximum Class Size 12
11 Minimum needed to run 8
12 Prerequisites/Co-requisites None
13 Who it is open to All postgraduate students

MSM 814 Statistical Reasoning for Educators MSc (Mathematics for Educators)

maybe need this 2nd year.

MSc (Mathematics for Educators)
Course code MSM 814
Course title Statistical Reasoning for Educators
AU value 3 AU
Name of instructor
Telephone
Email
Cheang Wai Kwong
6790 3920
waikwong.cheang@nie.edu.sg
Assessment mode Assignments and Tests

Time of day
Day of week
Date of first class
6 ± 9 pm
Friday
3 Sep 2010
Venue / Room

Math Lab 5 (7-B1-10) ± to be booked by AG

Specify the evening intake(s)
that is required to take the
course in Aug 08 Semester.
Programme/Specialisation:
Intake Year:
None
Maximum class size 25
Who it is open to? All MSc and PhD students who have good
background in statistics
Statistics I and II in NIE Degree programme)

SA 823 Academic Discourse Special Topic Courses

to take 2nd year. Special Topic Courses
http://teachers.nie.edu.sg/portal/page/portal/TeacherPortal/ContentDetails?paramMainTab=132¶mNodes=580

1 Course Code SA 823
4 Medium of Instruction English
5 Lecturer / Coordinator¶V
name, telephone no. &
e-mail
A/P Antonia Chandrasegaran
67903393
antonia.c@nie.edu.sg
6 Assessment Mode Text analysis (40%) & Essay assignment with
commentary (60%)

8a For classes meeting
regularly over approx 13
weeks

Time of Day
Day of Week
Date of First class

6 ± 9 PM
Tuesday
Tue of Week 1 of semester
8b Alternative Schedule -
9 Venue To be booked by GPR; room to have visualizer and
computer
10 Maximum Class Size 20
11 Minimum needed to run 5
12 Prerequisites/Co-requisites Students should be engaged in the writing of their thesis or
13 Who it is open to All postgraduate students

MAE800 Research Methodology in Applied Linguistics MA (Applied Linguistics)

may need to take this in 1st year.
MA (Applied Linguistics)
Course code MAE800
Course title Research Methodology in Applied Linguistics
AU value 3 AU
Name of instructor
Telephone
Email
Dr Hu Guangwei (coordinator)
6790 3484
guangwei.hu@nie.edu.sg
Assessment mode By assignments and quizzes

Time of day
Day of week
Date of first class
6:00pm ± 9:00pm
Wednesday

1 September 2010
Venue / Room

A computer lab equipped with SPSS will be needed
for Sessions 6 and 7. The preferred lab is the
Fourier Lab (7-B1-12).

A tutorial room in Block 3 is preferred for the rest
of the sessions.

Specify the evening intake(s)
that is required to take the
course in Aug 2010 Semester.
Programme/Specialisation:
Intake Year:
No
Maximum class size 25
Who it is open to? All MA (applied linguistics) students and PhD
students.
Prerequisites No.

MSM 814 Statistical Reasoning for Educators

Looks interesting but can't do Friday
http://teachers.nie.edu.sg/portal/page/portal/TeacherPortal/ContentDetails?paramMainTab=132¶mNodes=580

Course code MSM 814
Course title Statistical Reasoning for Educators
AU value 3 AU
Name of instructor
Telephone
Email
Cheang Wai Kwong
6790 3920
waikwong.cheang@nie.edu.sg
Assessment mode Assignments and Tests

Time of day
Day of week
Date of first class
6 ± 9 pm
Friday
3 Sep 2010
Venue / Room

Math Lab 5 (7-B1-10) ± to be booked by AG

Specify the evening intake(s)
that is required to take the
course in Aug 08 Semester.
Programme/Specialisation:
Intake Year:
None
Maximum class size 25
Who it is open to? All MSc and PhD students who have good
background in statistics
Statistics I and II in NIE Degree programme)

SE 808 Doctoral Seminar 1: Advanced literature review and analysis

Sugeested modules
SE 808 Doctoral Seminar 1: Advanced literature review and analysis
http://teachers.nie.edu.sg/portal/page/portal/TeacherPortal/ContentDetails?paramMainTab=132¶mNodes=580

Modules for
1 Course Code SE 808
2 Course Title
Doctoral Seminar 1: Advanced literature review and analysis
4 Medium of Instruction
Face-to-face and online tutorial
5 Lecture
name, telephone no. &
e-mail
Dr Ching Sing Chai and Dr Joyce Koh
67903286
Chingsing.chai@nie.edu.sg
6 Assessment Mode The grading for the above courses for students would comprise the following:
1. Active participation and in-depth contribution (15%)
2. Organising and leading assigned seminar (25%)
3. Final project (60%)
8a For classes meeting regularly over approx 13 weeks
Time of Day Day of Week Date of First class
ECL 5 6-9 pm Friday
3rd
September
8b Alternative Schedule
NIL
9 Venue
ECL 5
10 Maximum Class Size
15
11 Minimum needed to run 10
12 Prerequisites/Co-requisites It is preferable for students who have already decided their research focus
13 Who it is open to All Ph.D. students/ MA (by Research) associated with the
Education Cluster Academic Groups. Special permission from the course instructor is required if students from other areas are interested in signing up for these seminars.

My PhD proposal after inputs from my supervisor to be.

My PhD proposal after inputs from my supervisor to be. :)

Title:
Designing computer simulation to support students’ scientific visualization in Electromagnetism

Research problem: Students often find electromagnetism concepts difficult due to its abstract nature (Demirci, 2004). This is despite the use of computer simulations in physics classrooms to help students visualize concrete phenomenon at the abstract level (Rivers & Vockell, 1987). One possible reason could be the ways in which visual representations are used in many of these computer simulations (Lee, 1999). Science representations can be categorized into three levels: macro, sub-micro and symbolic (Gilbert, 2005). A deeper understanding of science necessitates seeing, imagining and constructing within and connecting these levels of representations (Levy & Wilensky, 2009). In other words, design of simulations should consider these levels of visualizations as foundational principles in simulation design to allow students to make sense of electromagnetism (Gilbert & Boulter, 2000).

Goal:
To design computer simulation that takes into consideration multiple levels of scientific representation to support students’ understanding of electromagnetism

Objectives:
1. To design simulations to support students’ understanding of electromagnetism using the different levels of scientific representation
2. To understand how simulations foster a deeper understanding of electromagnetism.

Research questions:
1. What design of simulation foster a deeper understanding of electromagnetism?
2. To what extent does the designed simulation foster a deeper understanding of electromagnetism?
3. How does the designed simulation foster students’ understanding of electromagnetism?
4. How do the three levels of representations, macroscopic, microscopic and symbolic promote understanding of the curricular model of electromagnetism?

This study will take an iterative approach to explore, design, implement and evaluate the design of computer simulation to foster deeper understanding of electromagnetism.

Reference:
Demirci, N. (2004). University Students'’Conceptual Difficulties About Electricity Amd Magnetism Concept.
Gilbert, J. K. (2005). Visualization in science education: Springer-Verlag New York Inc.
Gilbert, J. K., & Boulter, C. J. (2000). Developing models in science education: Springer Netherlands.
Lee, J. (1999). Effectiveness of Computer-Based Instructional Simulation: A Meta Analysis. International Journal of Instructional Media, 26(1), 71-72.
Levy, S. T., & Wilensky, U. (2009). Crossing levels and representations: The connected chemistry (CC1) curriculum. Journal of Science Education and Technology, 18(3), 224-242.
Rivers, R. H., & Vockell, E. (1987). Computer simulations to stimulate scientific problem solving. Journal of Research in Science Teaching, 24(5), 403-415.

Tuesday, June 22, 2010

My original concept for a Doctor of Philosophy ( PhD ) study

My original concept for a Doctor of Philosophy (Ph.D.) study
Title:
Leveraging on open source tool, Easy Java Simulation (Ejs) to design interactive virtual laboratory and advancing computational modeling in Physics education.
(A) Proposed Area of Research
Leveraging on open source tool, Easy Java Simulation (Ejs) to design interactive virtual laboratory and advancing computational modeling in Physics education.
General overview of area
Easy Java Simulations (Ejs) is an open source java code generator tool developed by Prof. Francisco Esquembre (Universidad de Murcia , Spain) for the conceptual learning of science. Ejs is designed for the purpose of allowing teachers and students to create (or modify) scientific simulations. The tool provides an easy to use graphical drag-and-drop interface to build the simulation so that teachers and students can concentrate on a small amount of code for the scientific models and relations, while the Ejs software tool manages most of the java programming techniques. Though I have little programming experience as a teacher, I have already created and remixed complex simulations for use by others by means of sharing on the Ejs community forum by Prof. Fu-Kwun Hwang (National Taiwan Normal University, Taiwan ). My physics teaching experience in a Junior College for 7 years, my Masters of Arts in Instructional Design and Technology (NIE, 2007) and informal & self directed learning with use of the Ejs tool with the community of Ejs expert-users, allows me to design virtual laboratory experiments for inquiry learning purposes.
The Open Source Physics Project and other rich library of simulation source codes provide the opportunity for finer customization of virtual laboratory to promote engagement of learning, allow student centered inquiry learning and computer modeling. I intend to customize a series of virtual laboratory simulations for the learning of electromagnetism and conduct case study educational research in secondary schools, with physics learners in the topic of electromagnetism, probably secondary 4 classes, during (not hopeful) or outside (hopeful) formal curriculum time. This research takes experimental group study approach with interviews, surveys to have an indication of the learners’ affective domains towards learning of physics through the research intervention lessons. For the virtual lab lessons is targeted at 10 weeks with 10 virtual labs lessons staggering between the schools existing practical lessons. Research into the design of the virtual labs and curriculum materials to support the learning is to be conducted. A co-design approach will be used to help the teachers take ownership of the research intervention. Where appropriate, students and teachers world view on practice, knowledge and modeling of physics will add to the data captured.

Identification of the relevant literature
There are interactive digital media, such as, java applets that allow users to manipulate variables to observe changes in the affected variables. Most are closed sourced, editing is not allowed and some are produced by commercial entities thus the sources as well as the simulations are closely protected for monetary gains. There is a small but increasing number of physics academia that ride the wave of internet collaboration in the creation of physics simulations and sharing through open source physics projects. These models and simulations are created by physics professors with their undergraduate targeted audience in mind thus, some level of finer customization is required to suit the specific educational objectives of high school physics syllabus. The Ministry of Education (sg) is well position to infuse meaningful learning through ICT by investing on suitable candidate to tap on the Ejs community and develop meaningful virtual laboratory in the learning of physics in high school. I am that person poised to lead the infusion of meaningful activities with use of technology especially in the area of Physics education.
My research is targeted on development of virtual laboratory simulation, to support and complement existing real life classroom and laboratory demonstrations. This Ejs tool uses existing java language that is very suited for creating powerful and realistic physics models, probably limited by the authors modeling and coding knowledge.
The open source architecture also allows physics learners to examine how the simulations are model. By modifying the modeling codes, Ejs can serve as an effective teaching and learning tool especially when students create their own remixed simulations in order to understand the concepts on how a physics phenomenon is modeled.
Being aware of the issues of school practices with over emphasis on national assessment and concerns of teachers needing to improve the efficiency of learning curriculum contents, a virtual laboratory intervention is a good fit as it does not deviate too much for current science laboratory practices. Modeling science is probably difficult to implement without the support of the school principal, teachers and syllabus articulating the need for it.
Thus, my research is an original piece of work because of my creation and remixing of virtual laboratory source codes customized to complement the physics curriculum in mainstream high school in Singapore. The instructional design of the virtual laboratory, the scaffolds and hints within the learning environment and the activities to guide the inquiry learning, are niche area which will lead on to the thesis preparation.
Key research questions
The research can be completed within the time period allowed because of my focus in the area of electromagnetism within the boundary articulate in MOE curriculum syllabus guide. I will manage the study to include only a few secondary schools pure physics and combined science classes depending on availability and teachers readiness. The key questions within my niche area are:
1. What does the designed virtual laboratories tell us about it’s affordance to support physics inquiry learning?
2. What is the appropriate blend of real life practical sets and virtual laboratory that can help the inquiry learning?
3. Did the virtual laboratories encourage students to develop good attitudes and affections towards learning, as compared to the teachers existing teaching practices.
4. Did the virtual laboratories encourage teachers to develop good attitudes and affections towards teaching?

Methodology
First component –Literature Review on the following
• Existing Web technology tools that can be virtual labs environments
• Learning theories in science education
• Curriculum practical design
• Educational psychology
• Affordance of real physics laboratory setup and virtual ones
• Need assessment
Second component – Development of virtual labs design and curriculum materials to support the learning of electromagnetism for secondary schools syllabus. ( involving practitioners and learners)
Third component – Rapid prototyping the curriculum and virtual lab materials with a few learners, consultation with community experts in the area of physics education and/or virtual lab designs.
Fourth component- Data collection
• Schools Leaders and Teachers will be approached to get their support.
• Discuss and check with the school whether they have existing real life demonstrations sets to allows some hands-on for learners. This will affect research question 2 (RQ2).
• Minimum professional development need to be conducted to level up low ICT maturity teachers to a point when they can conduct these lessons.
o Survey, interviews with the teachers involved on the research question 1 (RQ1)
• 3 schools will be selected for the study, discussions with teachers on the number of classes for the data collection.
• Preferably the same virtual labs sets can be used in different schools and different times, data collection may spread over 2 years.
• After 5 virtual practical lessons, spanning 10 weeks, after each lessons, students feedback are collected. Additional interviews will be conducted by the teachers and researcher to triangulate their attitudes and affections. At the 3rd and 5th lessons, students are to write a paragraph to describe their feelings towards learning in this context, as a process. (RQ3)
• Teachers will be conducing the lessons, their passion to continue or not, similar lessons for non examination semesters, whether their attitudes and affections towards teaching has changed? (RQ4)
Fifth component – Improving the proposed method.

Timescale/research planning
1st year go through 1 to 4 once
2nd year completed all electromagnetic induction virtual labs (5 of them)
3rd year start data collection
4th year analyse data plus additional data collection
5th year report completed.
Bibliography
Esquembre, F. (2004). "Personal Web page of Francisco Esquembre." Retrieved 10 November, 2009, from http://fem.um.es/.
Esquembre, F. (2007). "Easy Java Simulations." Retrieved 13/03/2007, 2007, from http://www.um.es/fem/Ejs/Ejs_en/index.html.
Hwang, F.-K. (2007). "NTNU Virtual Physics Laboratory." Retrieved 13/03/2007, 2007, from http://www.phy.ntnu.edu.tw/java/.

(B) What is the significance of your proposed research project?
This research is significant because it can contribute to the inquiry learning based virtual laboratory pedagogy that has the potential for advancing learner centered activities with technology. The suitable blend of real life practical setups with the virtual ones, uniting the best features of the real and virtual worlds, can transform the learning in the science of physics education. With the world struggling to educate its citizens, this research and its virtual labs can allow for virtual pathway for virtual experiential learning in the physics of electromagnetic induction and other topics. With the learning of science that is invisible to the naked eyes, these virtual labs can provide some form of representation that makes them visible.
There are currently not enough realistic and scientific learning environments, free to redistribute and legal to modify to suit each nations’ physics curriculum needs. My work will be significant to the world because it will be free of monetary charge to use, anyone is free to redistribute my work under condition of attribution and anyone is free to modify and remix to meet their learning and teaching needs.
In time to come, my research artifacts and learning environments will be used, remixed, by educators all over the world and used in physical and virtual classrooms for 21st century physics education.

http://66.7.205.91/~lookangc/index.php?topic=1038.msg2052#msg2052

PhD phd

Thursday, June 17, 2010

Ejs Open Source Magnetic Field Vector of 2 current carrying wires Model « on: November 06, 2009, 06:39:44 PM » posted from:Singapore,,Singapore

 http://weelookang.blogspot.sg/2010/06/ejs-open-source-magnetic-field-vector_17.html  Ejs Open Source Magnetic Field Vector of 2 current carrying wires Model   author: fu-kwun hwang and lookang https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_MagneticField2Wire.jar  https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_MagneticField2Wire.jar
Ejs Open Source Magnetic Field Vector of 2 current carrying wires Model
« on: November 06, 2009, 06:39:44 PM » posted from:Singapore,,Singapore
Ejs Open Source Magnetic Field Vector of 2 current carrying wires Model by Fu-Kwun Hwang and lookang
Individual and Resultant Force Magnetic Field of a wire and external magnetic field
reference:
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1273.msg4968#msg4968
Magnetic Field from 2 wires

The EJS Magnetic Field from 2 wires model computes the B-field created by an electric current through 2 straight wires in the z direction with the options of external magnetic fields. The user can click on any part of the 2D space to plot the magnetic field lines.

1. Watch the simulation as the field changes from the field around a long straight current-carrying wire to the field near a coil. Explain what happens to the field. Inside a coil of many loops, why is the field fairly uniform near the center (think about vector addition and what vectors would be adding together near the center).
2. There is an arrow on each end of the wire (red and blue). Which one shows the direction of the current in the wire? Explain.
3. The simulation also shows the magnetic flux. What is flux? Therefore, what do the different colors represent and why (i.e is pink higher flux than yellow or vice versa)? and what does "higher flux" mean in terms of the geometry and field strength?)?
Credits:

The Magnetic Field from Loops simulation was created by Fu-Kwun Hwang, edited by lookang using the Easy Java Simulations (EJS) modeling tool . Additional exercises written by lookang. You can examine and modify the model for this simulation if you have Ejs installed by right-clicking within the simulation frame and selecting "Open Ejs Model" from the pop-up menu. Information about EJS is available at: http://www.um.es/fem/Ejs/

Tuesday, June 15, 2010

Gearing up for the future video

Gearing up for the future video
http://ictconnection.edumall.sg/cos/o.x?c=/ictconnection/pagetree&func=view&rid=664

The underlying philosophy of the Masterplans is that education should continually anticipate the needs of the future and prepare pupils to meet those needs.

The video does not embed, though we have been telling the vendor to make it possible for public to share this video.

Hai..........
Test

Friday, June 11, 2010

Open source Ejs Magnitude of a vector java applet « on: May 26, 2008, 05:18:42 PM » posted from:Singapore,,Singapore

Open source Ejs Magnitude of a vector java applet
« on: May 26, 2008, 05:18:42 PM » posted from:Singapore,,Singapore

Magnitude of a vector Best java applet open source, made in EJS
http://home.phy.ntnu.edu.tw/~lookang/EJS_4.1_090115/weemagnitudeofavector03_Simulation.html
Magnitude of a vector Best java applet open source, made in EJS
kindly hosted in NTNUJAVA Virtual Physics Laboratory by Professor Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=674.0
alternatively, go direct to http://www.phy.ntnu.edu.tw/ntnujava/index.php?board=28.0
Author: lookang

Ejs Open Source Rectilinear motion of 2 objects java applet

 http://weelookang.blogspot.sg/2010/06/ejs-open-source-java-applet.html https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_catanddog.jar https://dl.dropbox.com/u/44365627/lookangEJSworkspace/exportarchived/ejs_catanddog.jar author: fu kwun and lookang
Ejs Open Source Rectilinear motion of 2 objects java applet
Ejs Open source java applet Displacement & Velocity time graph for area & dx/dt
« on: September 22, 2008, » posted from:Singapore,,Singapore

Open source Ejs applet Displacement & Velocity time graph showing relationships of area & dx/dt

http://home.phy.ntnu.edu.tw/~lookang/EJS/EJS_4.0_080905/weexva3/weexva3.html old version
http://home.phy.ntnu.edu.tw/~lookang/EJS/EJS_4.0_080905/weexva4/weexva4.html old
http://home.phy.ntnu.edu.tw/~lookang/EJS/EJS_4.0_080905/weexva10/weexva10.html
http://home.phy.ntnu.edu.tw/~lookang/EJS_4.1_090115/weexva10_Simulation.html

adapted from Two dogs running (set up xi,vi, and a ) http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=188.msg810#msg810

Displacement & Velocity time graph applet showing relationships of area & dx/dt

rate of change in displacement versus time at that time t = velocity at the same time.
Area of velocity versus time graph = distance traveled in Displacement time graph

exercise by lookang

for http://www.seab.gov.sg/oLevel/syllabus/5058_2011.pdf
2. Kinematics
Content
• Speed, velocity and acceleration
• Graphical analysis of motion
• Free-fall
• Effect of air resistance
Learning Outcomes:
Candidates should be able to:
(a) state what is meant by speed and velocity
(b) calculate average speed using distance travelled / time taken
(c) state what is meant by uniform acceleration and calculate the value of an acceleration using
change in velocity / time taken
(d) interpret given examples of non-uniform acceleration
(e) plot and interpret a distance-time graph and a speed-time graph
(f) deduce from the shape of a distance-time graph when a body is:
(i) at rest
(ii) moving with uniform speed
(iii) moving with non-uniform speed
(g) deduce from the shape of a speed-time graph when a body is:
(i) at rest
(ii) moving with uniform speed
(iii) moving with uniform acceleration
(iv) moving with non-uniform acceleration
(h) calculate the area under a speed-time graph to determine the distance traveled for motion with
uniform speed or uniform acceleration
(i) state that the acceleration of free fall for a body near to the Earth is constant and is
approximately 10 m/s2
(j) describe the motion of bodies with constant weight falling with or without air resistance,
including reference to terminal velocity

Prior Knowledge required
nil

Engage
1. How do you predict if the cat or the dog will reach the tree sooner? In physics, is it possible to estimate and predict which of the animal (cat or dog) will reach the tree first. There are some variables which you need to establish in order to predict. Can you list some the variables? Can you think of different ways to reach the tree?
hint: initial velocity vi, initial displacement xi (starting position), acceleration a .....

After some discussions, students can share their ideas through oral/verbal presentation.
Teacher can praise some of the ideas and point them to Ejs as a means to test (modeling approach) out their ideas using this Ejs simulation codes as templates for implementation.
Beginner Level:
Teacher can introduce the simulation to allow students to learn by experiencing.

Explore
1. Explore the simulation, this simulation is designed with a cat 1 and dog 2 moving in the x direction only between a house x = -100 m to a tree x = 100 m.
2 The play button runs the simulation, click it again to pause and the reset button brings the simulation back to its original state.
3 by default values, play the simulation. Notice that the top motion diagram (world view) shows the cat 1 and dog 2 moving in a straight line in the x direction. What is the physics principle(s) simulated here.Write down what you observe. Explain the motion in terms of the influences of initial displacement, initial velocity and acceleration for the whole motion.
_____________________________________________________________________
hint: newton's 1st law for dog 2 and newton's second law of cat 1
4 write down what does which of the slider represent or control?
for cat 1: x1i=______________, u1 =__________, a1=___________________
dog 2: x2i=_______________, u2=__________, a2=___________________
5 reset the simulation.
6 using the default values (x1i= =-100, u1=0, a1=12) and (x2i= =-100, u2=20, a2=0), play the simulation. write down the time for which the cat 1 reach the tree. ________________
7 select (x1i= =-100, u1=0, a1=0) and (x2i= =-100, u2=20, a2=0) and play the simulation.
write down the time for which the dog 2 reach the tree. ________________
notice that by making u1=0 and a1=0, the cat is stationary.
8 explore the slider x1i, u1, a1. what do these sliders control?
9 explore the slider x2i, u2, a2. what do these sliders control?
10 by leaving the cursor on the slider, tips will appear to give a description of the slider.
11 vary the simulation and get a sense of what it does.

12 reset the simulation and ignore the dog 2 for the steps below
13 predict what the graphs of displacement versus time and velocity versus time will look like for the following cases.
(i) at rest
(ii) moving with uniform speed
(iii) moving with uniform acceleration
*(iv) moving with non-uniform acceleration
14 select suitable values of the cat 1 for each of the cases above.
record down the values you suggested and explain why you choose them.
15 draw the graphs of displacement versus time and velocity versus time on paper with the prediction and observed plots of the cat 1 side by side. Are there any difference(s)? Elaborate on the difference(s) if any and discuss with their classmates. Consult your teacher if you need help.
16 by default values, play the simulation. select the checkboxes x1=x1f-x1i and x2=x2f-x2i at the top menu hint: what is displacement,x? suggest with reason, what is the meaning of displacement in terms of the (i) motion diagram and (ii) x versus t graph?
At the end of the simulation, notice the time slider is drag-gable for further exploration. Is your answer appropriate?
16 by default values, play the simulation. select the checkboxes x1=x1f-x1i and x2=x2f-x2i at the top menu hint: what is distance traveled? suggest with reason, what is the meaning of distance traveled in terms of the (i) motion diagram and (ii) v versus t graph?
17 Elaborate on what is the difference between displacement and distance traveled. You may explore the simulation to test your elaboration, if see if it is robust enough or is there a more precise way to describe them?
H
18 by default values, play the simulation. notice write down at the end of the simulation the values of for the following
displacement of cat 1, x1 = ______________
displacement of dog 2, x2 = ______________
distance traveled by cat 1, d1 = ______________
distance traveled by dog 2, d2= _______________
19 suggest suitable equations for this specific case.
x1 = ______________
x2 = ______________
d1 = ______________
d2= _______________
20 describe how did you arrived at the equation for d1 (cat under uniform acceleration) and d2 (dog under uniform velocity).
Optional:
21 how is dx/dt represented in the (i) motion diagram,(ii) x versus t and (iii) v versus t ?
hint: select checkbox what is dx/dt?
Evaluate:
22 A cat says to the dog "I will start with negative initial velocity and still reach the tree sonner than the dog that is running at constant velocity of 20 m/s" play with the simulation suggest suitable values of initial condition(s) and record systematically, determine if the cat is correct. State your assumptions made.

Have Fun!

Open Source Ejs Newton's First Law java applet « on: November 25, 2008, 05:45:08 PM » posted from:Singapore,,Singapore

 http://weelookang.blogspot.sg/2010/06/open-source-ejs-newtons-first-law-java.htmlhttps://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_FirstLawtrywee.jar https://dl.dropbox.com/u/44365627/lookangEJSworkspace/exportarchived/ejs_users_sgeducation_lookang_FirstLawtrywee.jar author: woflgang and lookang
Open Source Ejs Newton's First Law java applet
« on: November 25, 2008, 05:45:08 PM » posted from:Singapore,
,Singapore

Open Source Ejs Newton's First Law java applet
Newton's First Law EJS applet by lookang
adapted from F:\EasyJavaSimulation\EJS_4.1_081121\EJS_4.1\workspace\source\users\davidson\wochristian\newton_law"A body continues to maintain its state of rest or of uniform motion unless acted upon by an external unbalanced force." This law is known as the law of inertia. http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion

This has a lot of potential of students doing by modifying equations in EJS.
simple enough i hope!

PS: press "Enter" on the keyboard when keying in new values? The input field need to be white (registered by applet), if it is still yellow (unregistered), press "enter" on the keyboard

write up by Wolfgang Christian

Newton's First Law
Lex I: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.  (Isaac Newton 1687)
In 1687 Isaac Newton wrote in the Principia Mathematica "An object at rest will remain at rest unless acted upon by an external and unbalanced force. An object in motion will remain in motion unless acted upon by an external and unbalanced force."  This law implies that it is possible to select a reference frame, called an inertial reference frame, in which a free particle moves without any change in velocity. The First Law is often simplified as follows: An object in motion will remain in motion unless acted upon by another force.
What  is interesting about this Ejs model is that dragging the on-screen ball or the arrow automatically change the model's variables.  Double click on the green arrow in the Launcher table of contents tree to run the First Law model.  You can drag the particle to set its position and you can drag the arrow to set the particle's velocity.
The Ejs implementation of Newton's first law is very simple.  The Evolution workpanel merely advances the position and time.
x = x + vx*dt;
y = y + vy*dt;
t = t + dt;
Note that the equals sign does not represent mathematical equality when used in Java code.  The equals sign is a replacement operation that says:  "Replace the value on the left hand side with the value of the expression on the right hand side."
References:
The First Laws model is  a designed to teach Ejs modeling.  Right click within the simulation to examine this model in the Ejs modeling and authoring tool.  See:
"Modeling Physics with Easy Java Simulations" by Wolfgang Christian and Francisco Esquembre, The Physics Teacher, November 2007, 45 (, pp. 475-480.
The Easy Java Simulations (EJS) manual can be downloaded from the ComPADRE Open Source Physics collection and from the Ejs website.
Note:
This simulation was created by Wolfgang Christian using the Easy Java Simulations (Ejs) modeling tool. You can examine and modify this simulation if you have Ejs installed by right-clicking within a plot and selecting "Open Ejs Model" from the pop-up menu.
Information about Ejs is available at: .

The First Law model was built with the Easy Java Simulations (Ejs) modeling tool.  Ejs is a Java program that enables both programmers and novices to quickly and easily prototype, test, and distribute packages of Java simulations. It can be downloaded from the Ejs website and installed (unzipped) into a directory of your choice.
http://www.um.es/fem/Ejs
An important feature of the programs in the jar file is that it was created in such a way that users can return to the Ejs authoring tool at any time to examine, modify, and adapt the Ejs models.  Right-click within the simulation and select Open Ejs Model to invoke this feature.  (You must, of course, have already downloaded and installed Ejs.)  The Ejs authoring tool will appear.

My contributions are
1. a slider time bar variable t...............yes!! i finally made one myself thanks to prof Hwang's comment about thinking about how to implement it in EJS.

2. ODE equation dx/dt = vx, dy/dt = vy instead of the equations originally

3. panel for inputs of variables like vx and vy so that students can explore when if scenarios

Ejs Open source Circular Motion and Centripetal Force java applet F = m*v^2/r « on: December 12, 2008, 02:14:55 AM »

 http://weelookang.blogspot.com/2010/06/ejs-open-source-circular-motion-and.htmlEjs Open source Circular Motion and Centripetal Force java applet F = m*v^2/rhttps://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_CircularMotion_Circularmotion347.jarauthor: fu-kwun hwang and lookang
Ejs Open source Circular Motion and Centripetal Force java applet F = m*v^2/r
« on: December 12, 2008, 02:14:55 AM »

Circulation Motion and Centripetal Force applet modified for F = m*v^2/r lookang
Ejs Open source Circular Motion and Centripetal Force java applet F = m*v^2/r

applet modified legally under from http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=693.msg2488#msg2488
Circular motion: acceleration always perpendicular to velocity

MIT video
http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/embed05/

Ejs Open Source Kepler System Model by Dr. Todd Timberlake « on: April 05, 2010, 12:24:28 AM »

update 23 may 2013

Ejs Open Source Kepler System Model by Dr. Todd Timberlake
« on: April 05, 2010, 12:24:28 AM »

Ejs Open Source Period of Planets Model T^2 proportional to r^3 by Dr. Todd Timberlake

Kepler System Model written by Dr. Todd Timberlake
Access Rights: Free access
Rights Holder: Todd Timberlake
Keywords: EJS, Earth, Easy Java Simulations, Kepler, OSP, Open Source Physics, Sun, celestial globe, celestial sphere, elliptical, orbit, orbit
reference:
The Kepler System model simulates Kepler's final theory of planetary motion. In this theory the planets orbit in ellipses with Sun at one focus (Kepler's First law). These elliptical orbits are not necessarily all in the same plane. A line from Sun to the planet sweeps out equal areas in equal times (Kepler's Second law). The square a planet's period is directly proportional to the cube of the semimajor axis of its elliptical orbit (Kepler's Third law). The simulation shows Earth's orbit around Sun, as well as the orbit of one other planet. The user can choose to show one of the five visible planets (Mercury, Venus, Mars, Jupiter, or Saturn), or a fictitious planet. The top window shows the orbits of the planets around Sun. The view can be changed by clicking and dragging in the window and a zoom slider is provided to zoom in or out. The bottom window shows the view of Sun and planet against the background stars as seen from Earth.

i will be remix this into applet for the inquiry based learning of F=GMm/r^2 and T^2 proportional to r^3 based on data.

Simulation above is kindly hosted by NTNUJAVA Virtual Physics Laboratory by Professor Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1501.0
alternatively, go direct to http://www.phy.ntnu.edu.tw/ntnujava/index.php?board=28.0
Author: Todd Timberlake and remixed by lookang

Ejs Open Source Ideal Hard Disk Gas Model by Wolfgang Christian « on: March 18, 2010, 05:31:44 PM » posted from:Singapore,,Singapore

Ejs Open Source Ideal Hard Disk Gas Model by Wolfgang Christian
« on: March 18, 2010, 05:31:44 PM » posted from:Singapore,,Singapore

This is a legally remix applet license under GNU General Public License (GPL) version 2 http://www.opensourcephysics.org/misc/copyright.html , but please note that the narratives of books, manuals, and curricular material associated with this code are copyrighted by the authors and/or publishers which are not here anyway Smiley
Ejs Open Source Ideal Hard Disk Gas Model by Wolfgang Christian java applet remixed by lookang
Reference:
Ejs Open Source Ideal Hard Disk Gas Model by Wolfgang Christian http://www.compadre.org/osp/items/detail.cfm?ID=7573

i don't think i got the physics codes correctly implemented for e !=1

Phet The Moving Man

 Click to Run
Embed an image that will launch the simulation when clicked
Use this HTML code to display a screenshot with the words "Click to Run".

There is an abandon version here, feel free to edit it into a better applet
 Ejs Open Source Position, velocity, and acceleration graphshttps://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_position.jarauthor: lookang

Ejs Open Source Position, velocity, and acceleration graphs
« on: March 12, 2009, posted from:Singapore,,Singapore

Open Source Ejs Superposition of 2 Waves generated by equations « on: January 28, 2009, 11:15:07 PM »

 http://weelookang.blogspot.com/2010/06/open-source-ejs-superposition-of-2.html 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. https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_WaveFunctionPlotterSuperpositionwee01.jar https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_WaveFunctionPlotterSuperpositionwee01.jar author: wolfgang and lookang worksheets by (lead) SRJC:https://www.dropbox.com/s/uslrrrdkyq2puqe/WavesSRJC.zip
 new features added. (1) create a 1/8 step of the period (2) make 8 squares for 2 waves (3) added two pointers on progressive waves. thanks to joshua yeo and chew ling

Open Source Ejs Superposition of 2 Waves generated by equations
« on: January 28, 2009, 11:15:07 PM »

Open Source Ejs Superposition of 2 Waves generated by equations

http://home.phy.ntnu.edu.tw/~lookang/EJS_4.1_090122/WaveFunctionPlotterSuperpositionwee.html

adapted from C:\EJS_4.1_090122\EJS_4.1\workspace\source\ModelingScience\Ch03_Basics\WaveFunctionPlotter.xml by Wolfgang Christian and Francisco Esquembre using the Easy Java Simulations (EJS) version 4.1 authoring and modeling tool.

Full screen applet v1
Full screen applet older
Java Simulation above is kindly hosted by NTNUJAVA Virtual Physics Laboratory by Professor Fu-Kwun Hwang http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=906.0 alternatively, go direct to http://www.phy.ntnu.edu.tw/ntnujava/index.php?board=28.0 Collaborative Community of EJS (Moderator: lookang) and register , login and download all of them for free :)
Author:   Wolfgang Christian and Francisco Esquembre and lookang (this remix version)

Ejs Open source java applet Resolving a Vector in 2 perpendicular directions « on: March 01, 2009, 01:04:14 AM »

to answer question on moving down a slope
 acceleration along the slope is g sin $\theta$http://weelookang.blogspot.sg/2010/06/ejs-open-source-java-applet-resolving.htmlhttps://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_sinecosinewee03.jarhttps://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_sinecosinewee03.jarAuthor: Fu-Kwun and lookang
 acceleration along the slope is g sin $\theta$

EEjs Open source java applet Resolving a Vector in 2 perpendicular directions
« on: March 01, 2009, 01:04:14 AM » http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1018
Resolving a Vector in 2 perpendicular directions by lookang
original source code by hwang fu-kwun, remixed for helping visualization of components
reference:
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=634.msg2195#msg2195
http://www.walter-fendt.de/ph14e/forceresol.htm
kindly hosted in NTNUJAVA Virtual Physics Laboratory by Professor Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1018.0
alternatively, go direct to http://www.phy.ntnu.edu.tw/ntnujava/index.php?board=28.0
Author: Fu-Kwun and lookang

Add two vectors to determine a resultant by a graphical method ( A + B = R ) « on: March 05, 2009

Updated 31 july 2015

Example 1 |V₁|=120,ϑ₁=60°,|V₂|=80,ϑ₂=115°

Add two vectors to determine a resultant by a graphical method ( A + B = R )
« on: March 05, 2009,  posted from:Singapore,,Singapore

reference:
Summation of vectors
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=216.msg846#msg846
Add two vectors to determine a resultant by a graphical method
taken from http://www.seab.gov.sg/SEAB/oLevel/syllabus/2009_GCE_O_Level_Syllabuses/5058_2009.pdf

work in progress.....

and then for
taken from http://www.seab.gov.sg/SEAB/aLevel/syllabus/2008_GCE_A_Level_Syllabuses/8866_2008.pdf

kindly hosted by NTNUJAVA Virtual Physics Laboratory by Professor Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1022.0
alternatively, go direct to http://www.phy.ntnu.edu.tw/ntnujava/index.php?board=28.0
Author:  Fu-Kwun and lookang

Ejs Open source Newton's Cradle java Applet by Paco customized by lookang « on: December 17, 2008, » posted from:Singapore,,Singapore

Ejs Open source Newton's Cradle java Applet by Paco customized by lookang
« on: December 17, 2008,  » posted from:Singapore,,Singapore

Open source Newton's Cradle Applet by found in EJS 4.1 user/murcia/fem/mechanics
Ejs Open source Newton's Cradle java Applet by Paco customized by lookang

Ejs Open Source Roller Coaster Physics Model Java Applet « on: April 15, 2009, » posted from:Singapore,,Singapore

Ejs Open Source Roller Coaster Physics Model Java Applet
« on: April 15, 2009,  » posted from:Singapore,,Singapore

taken from Michael Gallis writeup
This applet simulates motion along a constrained path, such as what a roller coaster would take (assuming it has safety wheels to keep it on the track in “up-side-down” situations, of course). The simulation offers a chance to explore a number of concepts associated with roller coaster physics, including conservation of energy, reaction forces, motion in a vertical plane and friction. There are a number of example tracks which can be accessed via the drop down menu. Each of the tracks may be modified by dragging the control points which are visible when the simulation is paused. The user can also specify the coaster's initial speed (v0) which in turn affects the total energy of the coaster. The user can also input the strength of the aerodynamic friction force via the constant k. The friction force is given by Ff =-kv. The speed of the simulation can be modified by changing the calculation time step dt. The simulation tracks the roller coaster car's kinetic energy (KE), potential energy (PE) and mechanical energy (ME) which is the sum of KE and PE. If the car is subject to friction, thermal energy (TE) is also tracked to represent the "lost" mechanical energy.

The user can also manipulate the tracks by means of control points when the simulation is paused. Select a track to edit from the drop down menu. For the custom track, the user can also specify the number of control points for the track in edit mode by changing N at the bottom of the window

Custom tracks can be saved by right-clicking on the window selecting Save State. The custom track can be loaded by right clicking on the window and selecting Read State.

Michael Gallis is the original creator, i only remixed it, refined it and fixed some bugs in the drop down menu

kindly hosted by NTNUJAVA Virtual Physics Laboratory by Professor Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1088.0
alternatively, go direct to http://www.phy.ntnu.edu.tw/ntnujava/index.php?board=28.0
Author: Michael R. Gallis, Wolfgang Christian and lookang
Content: Barbara Christian, Anne Cox, and Mario Belloni

YouTube. Was stuck at Portland airport from 11pm to 4am, decided to use the time to make some promotional video on the applets shared during 2010 AAPT Summer Meeting in Portland, Oregon

original writeup by Michael Gallis

A roller coaster traveling on a track under the influence of gravity. Bar graphs show the potential energy (PE), kinetic energy (KE) and total mechanical energy(E) of the car. You can drag the blue points on the track to new positions to change the shape of the track. Click on the document button  to get an activity worksheet.

Activities:

Energy

The mechanical energy (ME) of the car is the sum of its kinetic energy (KE) and its potential energy (PE). The car's ME is determined by its initial height of the car and its initial speed (the initial speed defaults to zero). The initial potential energy (PE) is determined by the height of the start of the track, determined by the first control point of the track. Select the up and down example and then select edit track. Change the starting height of the track. What happens to the mechanical energy ME and the potential energy PE? Start the simulation by hitting the play button. How far up the other side of the track does the car get? How does the maximum height attained by the car on the right side of the track depend upon the initial height of the car? What happens to the mechanical energy when you change the initial speed?
Select the single loop example track and then select edit track. What happens to the total energy E and the potential energy PE as the initial height is changed? When the simulation is played, what happens to the motion of the car when the initial height is changed? Is there a relationship between the initial height of the car and the size of the loop when the car barely makes it around the loop?

Aerodynamic drag (friction) can be introduced by setting the drag coefficient to something other than zero. Values around .1 to .5 are good starting points. Pick one of the example tracks, set the friction coefficient to .20. What happens to the energy? When does it change the fastest? Where does the energy "go" in a real coaster? When the coaster is subject to friction, it "loses" mechanical energy ME, and the simulation tracks that loss as thermal energy TE.
You can set the coefficient in this simulation to a negative number. Try setting k to -.20 and run the simulation. Why is such a situation "unphysical"?

Reaction Forces

Start with the "up and down" track and then select edit track. Move the control points to create a ramp that levels out, as shown above. Play the simulation and observe the reaction force at different parts of the track. This reaction force corresponds to “how heavy the rider feels”. Change the steepness of the left side of the track and observe the changes in reaction force. Is it possible to get the reaction force to be exactly zero? What would zero reaction force feel like in the “real world”?

Change your ramp track into a fairy symmetric U shape, as shown above. Play the simulation and observe the reaction forces.
Now make the bottom part of the track narrower by moving the bottom control points closer together (as below). What happens to the reaction force?

Select the loop example track and play the simulation. Where on the loop is the reaction force greatest? Where is it the least? Now lower the starting height for the car so that the reaction force at the top of the loop is as small as you can make it. (This will have to be done by trial and error.) What would this feel like to a rider? Now adjust the starting height to be as low as possible and still have the car make it around the loop. What happens in this case to the reaction force at the top of the loop? What would this feel like to the rider, and is he glad he buckled his seat belt?

1. Play the simulation and watch what happens to the bar graphs. When is the kinetic energy (green) bar the maximum? When is the potential energy (purple) bar the maximum? How does the total energy (E) bar change? Does its height change? Explain.
2. Stop the simulation. Use the "Steps the Simulation" button to step the simulation. Sketch the bar graph and position of car on the track to show maximum gravitational potential energy. Do the same to show maximum kinetic energy.
3. Place the cross hairs on the car to find the height. Record the height and velocity of the cart at the maximum potential energy and maximum kinetic energy. Assume the car's mass is 1 kg. Calculate PE when velocity is zero. Calculate KE when height is zero. Do your answers make sense? Why?
4. Select a new track from the drop down menu. Sketch the car on the track at various positions and use the heights of the graphs to show that mechanical energy is conserved.
5. Advanced: Try the simulation where you add friction (click the Friction checkbox). What happens to the energy bar graphs? Why? Form a hypothesis about when mechanical energy is conserved.

Dynamics

Notes for Roller Coaster Applet

The coaster follows a path described by a parametric curve [x(s),y(s)], so that the coaster's position along the path can be described by the single variable s. Lagrangian mechanics can be used to determine the equations of motion. The kinetic energy is given by
KE = 1/2*m*v^2 = 1/2*m(x'^2+y'^2)
where primes indicate differentiation with respect to s and dots indicate differentiation with respect to time (t).
The potential energy is given by
PE = m*g*y
and the Lagrangian is given by L = KE-PE.
Lagrange's equation
d/dt(dL)/ds dot - dL/ds = 0
yields
m(x'^2+y'^2)s'' + m(x'*x''+y'*y'')s'^2 + m*g*y' = 0

The dynamics are integrated numerically using Euler's Method:
?

To add frictionto the dynamics, Rayleigh's dissipation function F is added (see Goldstein's Classical Mechanics, e.g.) where
?
The modified Lagrange Equation becomes
?
which yields
?
or
?

Because round off error in the numerical integration is significant, and because energy conservation is one of the principles being illustrated, kinetic energy is adjusted each iteration to ensure the total energy constant. At each iteration, the work done by friction is

so that for each iteration the total energy is "adjusted" by taking E = E+dWf. Finally, the "speed" of the particle is adjusted at the end of each iteration to ensure the energy is correct ( T + V = E ):
PE=g*ys(coaster_s);
E=Math.max(PE,E-k*(xsp(coaster_s)*xsp(coaster_s)+ysp(coaster_s)*ysp(coaster_s))*coaster_sv*coaster_sv*dt);
KE_est=E-PE;
if(KE_est>=1.0E-6) {
KE=.5*(xsp(coaster_s)*xsp(coaster_s)
+ysp(coaster_s)*ysp(coaster_s))*coaster_sv*coaster_sv;
coaster_sv=coaster_sv*Math.sqrt(KE_est/KE);
}

The reaction force is estimated from the acceleration of the coaster and the force of gravity. However, only the component of the reaction force estimate that is perpendicular top the track is shown in the simulation.

The friction force is shown, but it will generally be small in magnitude compared to the other forces. This may be a nuisance visual.

Credits:

This simulation was created by Michael Gallis and modified by Wolfgang Christian using the Easy Java Simulations (EJS) modeling tool. You can examine and modify this simulation if you have Ejs installed by right-clicking within a plot and selecting "Open Ejs Model" from the pop-up menu. Information about Ejs is available at: <http://www.um.es/fem/Ejs/>.