hi every one .. as you can see below on the image on the attachments ,, this is my project paper ... i have already solve 80 % percent of the project ,, but there is one problem that i cant find solution for it ... maybe it is the easiest part ,, but my knowldge on math and movment equations is too bad :)(adsbygoogle = window.adsbygoogle || []).push({});

any way ,, my problem is how can i know the new direction for the particle when it is reach the boundary ( border of the circle ) the direction is represented as angle ,, so how can i know the new angle ( direction ) for a specific particle that is reflected because it is reaching the boundary !!!

sorry my english is not good , but i hope you can at least understand what i mean :)

thanks alot

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# How to solve This Problem !

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