on: August 02, 2010, 12:29:48 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

Ejs Open Source Gravitational Field & Potential of 2 Mass Java Applet many thanks to Professor Andrew Duffy for his original codes http://www.compadre.org/osp/items/detail.cfm?ID=9411 , to Professor Fu-Kwun Hwang for his forum and community of learners & to Professor Paco for creating Ejs toolkit. Professor Wolfgang for OSP codes.

Reply #1 on: August 02, 2010, 12:33:02 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

remixing it for gravity field and potential work in progress

1 convert all variables to mass 2 convert constant to G 3 redraw the position of the force 4 introduce range and rangey to make the mass always appears as a circle as a function of the xmax, xmin, ymin, ymax used by applet 5 trying to convert the symbolic representation to mass type from electric type 6 added ODE to make test mass move according to d(xtest)/dt = vxtest & d(vxtest)/dt = g_net 7 added code to make vxtest=0 when slider move or xtest drag etc. 8 change all text to gravity instead of electric. 9 added Fnet = mtest*g 10 added U = mtest*ø

10 play button for ODE to run 11 added slider from text mass 12 changes are made based on an applet by Andrew Duffy http://physics.bu.edu/~duffy/classroom.html is the creator of his original applet. 13 closer remix was based on http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1918.msg6989#msg6989 12 May 2011 added 0.00 E-08 to all readings to make it as calculated by calculator July 2011 made the slider to include input fields for exact value of mass = 300 kg for example some slight adjustment of the check-box 03 august 2011 added step () button move checkbox to left of bar value for both potential and field to reduce space taken up by the words for the checkboxes

To do. May need one customized to real earth and moon data Mass of Earth = 6.0 x 1024 kg Radius of Earth = 6.40 x 10^6 m

Mass of Moon = 7.35 x 10^22 kg Radius of Moon’s orbit = 3.84 x 10^8 m

Time for Moon to complete one orbit around the Earth = 2.36 x 106 s

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« Last Edit: August 03, 2011, 01:40:08 pm by lookang »

Reply #2 on: March 09, 2012, 03:11:33 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

discussion with teachers

G field strength & potential - please add a button to reveal and hide the g field strength and potential value bars - make colour change of g field value bar to reflect +ve and -ve values. - make -ve sign more visible if possible - dotted lines to trace the test mass to graphs (g field & potential) and to vertical axis - analysis tool to reveal the gradient of tangent to potential graph and g field strength

Reply #4 on: March 12, 2012, 03:10:21 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

updated!

changes include

redesign the way g and V are plotted by combining into a graph for ease of data analysis tool with a blocker to block the middle line made the mathematical representation without * improve the scale to draw force move g and V to the right side and made to scale add indicator lines for both g and V add data analysis tool for investigation of dV/dx = - g for any point x

Reply #5 on: April 27, 2012, 12:45:30 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

need to have discussion with teacher F2F before i implement the changes

1) Can we have the arrow scale slider permanently displayed, instead of hiding in the green check box? added permanent on the left

2) Can we have the two arrows along the same line, instead of one above another? the purpose is to allow visualization when both are perfectly align it is hard to see. i make it slightly apart still acting of the particle, should be better now.

3) Can we also hide Mass 1 and display only Mass 2? This will help students observe the individual g and potential graphs before they observe the net g and potential graphs. agree, done

4) Can we have a button to hide the g field arrows? So that the arrows won't confuse the students when they are observing the potential graphs. agree, done

5) Is it necc to have the Fnet and Unet? I suggest remove the green and transparent check boxes. to complete the computer model to allow inquiry into the Fnet and Unet. i recommend keep them for students to understand

6) Can we indicate 'g' beside the g graph check box? same for potential graph check box. agree, done

7) Mass 1 and Mass 2 sliders and display boxes are just next to each other and the same blue colour may make it difficult to differentiate. Can you demarcate the two with a thick solid line. agree, done

Can we have a button to display a tangent for potential graph? The gradient of tangent should be equal to the - (g value). Good to display the value of gradient and g value simultaneously for comparison. agree, done made dV/dr = to show to be compare to g. for realization of dV/dr = - g. the minus sign is to be included by students to deepen thinking.

Reply #6 on: May 07, 2012, 08:22:47 am » posted from:SINGAPORE,SINGAPORE,SINGAPORE

changes made:

made the mathematical representation consistent for mass1 to be not shown. add scale1 to make the formula consistent gy= k*q1*scale1/((xtest-x1)*(xtest-x1))*(xtest-x1)/Math.abs(xtest-x1)+ k*q2*scale2/((xtest-x2)*(xtest-x2))*(xtest-x2)/Math.abs(xtest-x2); Vy = k*q1*scale1/(Math.sqrt((xtest-x1)*(xtest-x1)))+ k*q2*scale2/(Math.sqrt((xtest-x2)*(xtest-x2)));

Reply #7 on: May 07, 2012, 04:36:03 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

discussion with teacher

1) there is a small circle below the test mass. I think the circle is meant for potential graph. Can the circle only appears when the potential graph is checked, to reduce distraction? Thanks.

2) right now, the g field arrow only appears when we check the g button and then check the g1 button. Actually I would like the students to visualise the arrows first without looking at the graph. Furthermore, when we uncheck the g button and check the V button, the arrow still appears because the g1 button is not unchecked. Can we have another button to activate the g arrows? and the arrow for the particular M will appear as long as the g arrow button is checked and the M button is checked. Thanks.

3) can we make it such that the g2 bar (on the right side) only apears when the M2 button is checked? because it is causing distraction and serves no purpose if M2 is not present. Similarly the g net bar should only appear when both M1 and M2 buttons are checked simultaneously. What do you think?

4) the tangent for dV/dr is nice, although I think the value is fake. but it provides good visualisation for our students. Just one small request, the dV/dr value has a 'E08' placed very far to the right. Students may not notice it. Can we reduce the length of the value display bar?3

can you standardise the symbol for potential because the sim uses both V and greek symbol 'phi'.

« Last Edit: May 07, 2012, 04:38:22 pm by lookang »

Reply #8 on: June 02, 2012, 08:31:52 am » posted from:SINGAPORE,SINGAPORE,SINGAPORE

More discussion NO time to change yet.

For the attached simulation, I notice that the potential is labelled as V. Can you change it to the 'phi' symbol for all?

done using

Code:

math_failure (math_unknown_error): \\phi

Also can I suggest that the g field strength arrow/s appear automatically when the g button is clicked and M1 or/and M2 is clicked?

done

Instead of having to check the box on top of the g field strength bars (on the right of the screen). What happen now is that the students may have unchecked the g button but the g arrows are still around because they have not unchecked the box on top of the g field strength bars.

« Last Edit: June 08, 2012, 02:21:32 pm by lookang »

Reply #9 on: June 08, 2012, 01:33:48 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

More discussion

For the "Gravitational Field and Potential in One Dimension Model", could he make it such that if the central button for potential "v" is NOT clicked, the tick box for dv/dx will also automatically be unticked? I initially was confused at how come there was a gradient line but it didnt follow the g-field plot. [OK, i was not following instructions in the worksheet, but playing around on my own]

Reply #10 on: June 11, 2012, 10:55:31 am » posted from:SINGAPORE,SINGAPORE,SINGAPORE

discussion

Now I'm looking at the checkbox for the "?" at the lower right hand corner. In the pop-up window, the last set of instructions [to click on graph area>Select Elements options - PlottingPanel - DataAnalysis to verify dg = - d/dr] . . . i cant find DataAnalysis after the PlottingPanel. Also, should it be g = - d/dr ?

done, i have removed Data Analysis and replace with the phi and d(phi)/dr check box and display for more immediate concept-trend generalization after discussion with teacher(s)

Also, i noticed the displayed values for d/dr is always kept to 2 dp. But the bar is exceptionally long. Verifying manually, i missed out the E-08 at the end initially. If it's not too much trouble already, could you help me reduce that box length sincethe values are already constrained? done

Reply #12 on: June 28, 2012, 08:17:32 am » posted from:SINGAPORE,SINGAPORE,SINGAPORE

changes

added time to allow a sense of passage of time especially when m1 is moving and simulation pause when m1 hits M1 or M2 improved collision detection and pause //case 2 inside mass1 if (show1==true&&xtest <(x1+size/2)&&xtest>(x1-size/2)) { _pause(); } //case 3 inside mass2 if (show2==true&&xtest <(x2+size/2)&&xtest>(x2-size/2)) { _pause(); }

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