Hello Mr. Hwang,

thank you for the nice simulation.

I would like to ask for some extensions.  :)

First, I would like to add the bounce with the raquet to the simulation. I mean, to add some graphs where we could observe the value of the forces/speeds developed between the ball and a blocking raquet, all along the trajectory after the bounce. Most interesting would be the relative velocity between the ball and the paddle surfaces. 

So I would like to give some input. Please see below a realistic representation of what happens when the ball impacts the rubber on the raquet. I am cuirous thinking on how this could be abstracted.

[img]http://mesatenista.net/mitidieri/_img239.jpg[/img]


And here, a squetch of what I am thinking about:

[img]http://mesatenista.net/mitidieri/blocks.gif[/img]

The red arrows represent the angle with which the ball leaves the raquet. The green arrows are the tangents to the trajectory.

Second, we could have graphs below the simulation showing the (i) initial module of the red vectors (as if a raquet was there with a fixed angle), (ii) of the relative speed between the ball and the raquet surfaces at the contact point (agian, as if a raquet was there with a fixed angle), (iii) variation of the angular speed with time/position.

We could also have the choice of fixing the position of the raquet and then run the simulation of the incoming/returning ball. 

I hope I am not being too much eager.

Best regards,

Carlos