Solve 2 coupled 2nd ODEs and plot them with ParametricPlot?

GROUPS:
 I am interested to solve two coupled 2nd order differential equations and plot the solution using ParamatricPlot. Can anyone help me to resolve this issue? The solution is a trajectory of a particle under the influence of gravity. So, I am also interested to animate the trajectory of the particle as well. I have attached the Mathematica script with this post. Attachments:
18 days ago
13 Replies
 Hi, maybe you can apply the programming concepts from the Trott Springs Example?
18 days ago
 Thanks for your response. I shall go through the Trott Springs example. However, I have not yet found any mistake in the Mathematica notebook that I attached with the previous post. Do you see any obvious mistake in that script?
18 days ago
 After correcting a typo (NDSolve) I got an error message NDSolve::derlen: The length of the derivative operator Derivative[2] in (x^\[Prime]\[Prime])[t] is not the same as the number of arguments. 
18 days ago
 What was the typo ? Do you understand the message you received ?
18 days ago
 The S was left out of NDSolve. I don't understand the error msg.
18 days ago
 Mariusz Iwaniuk 1 Vote After correcting works fine: Attachments:
18 days ago
 Now I have made all the corrections. It is working fine. Thank you once again. Can you please let me know the way to animate the curve ? E.g. a solid circle is moving and as it moves forward a red lines is drawn. Hope I am clear enough.Soumen
18 days ago
17 days ago
 Dear Mariusz, Thank you once again. The animation that you shared in your past post is exactly what I wanted. However, I am unable to reproduce the same using the mathematica notebook ("testplot ver2.nb"). It does not show the black dot and the curve near the point (x=1,y=0) fluctuates. Do you have any idea about the origin of this problem ? Kindly confirm if you have the correct notebook file.Regards Soumen
17 days ago
 I corrected Mathematica notebook.In Animate function we can't start T from 0, because Mathematica gives error message.Workaround is gives a very small number (10^-15). Attachments:
 Dear Mariusz Iwaniuk, Thanks for your response. Following your response I have made necessary corrections in my notebook. However, I still find error messages. Can you share your Mathematica notebook file? NDSolve::ndnum: Encountered non-numerical value for a derivative at t == 0.. >> `Regards Soumen