I want to know how to kill yourself without any pain?

I'm NOT committing suicide, this is for a paper i have to write in my personal and family development cl. There has recently been a lot of suicides in my town. We have to choose a method of suicide and write about the cause and effect of doing so. I would like to choose one that involves no pain, or one that could be done within an hour. I do not like bloody gory things.