When should I use 里 and 中？

大家好！

I am never too confident when trying to translate something like the following into Chinese:

• In humankind's history, there has yet to be a man who has gone to Mars. 

My problem is specifically the ‘in ________' part.  It seems to me that when speaking Chinese, sometimes 里 and 中are both used to represent something in progress, or to define a period of time.  For example:

1.       电影里的暴力镜头violence shown in films.

2.       那次军事体育比赛中，During that military sports competition,

I would like to know，is there a difference between 里 and 中 in these kinds of cases?  It seems to me that 中 is more for events that are processes, but I have no idea if that is right or not.

首先谢谢你们！