i have recreated this simulation here

trying embeding codes
<iframe width="750" height="750" src="https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_model_projectile2cannon/projectile2cannon_Simulation.xhtml" frameborder="0"></iframe>

enjoy!

and thanks a million to Professor Fu-Kwun Hwang for being a great teacher who taught me how to use EJSS to model physics!

read about the answer here
http://weelookang.blogspot.sg/2015/02/ejss-2-cannon-aim-at-each-other.html

or run by clicking here
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_model_projectile2cannon/projectile2cannon_Simulation.xhtml

or download the model and source codes in the attachments!

enjoy!