Through the model selected by the students, it gives an indication of the students prior knowledge about what they know now, so that the teacher can understand the gaps of understanding for personalised mentoring Interesting Fact 2 This app is produce real numbers to coincident with the real world data of gravity pull at 9.81 m/s^2 with some random errors simulating real data-logger results. There is a mathematical modelling pedagogy built into the simulation for students to make effort to represent the physics similar to Tracker's particle modeling. Acknowledgement My sincere gratitude for the tireless contributions of Francisco Esquembre, Fu-Kwun Hwang, Wolfgang Christian, Félix Jesús Garcia Clemente, Anne Cox, Andrew Duffy, Todd Timberlake and many more in the Open Source Physics community. I have designed much of the above based on their ideas and insights, and I thank the OSP community for which Singapore was honored with 2015-6 UNESCO King Hamad Bin Isa Al-Khalifa Prize for the Use of ICTs in Education.