i'm not trying to be a dick or anything, but you need to take a look at the mechanism. Your ability to coast and line up the cranks to provide stopping power help as well. There are two brake shoes inside the hub of a coaster brake, and when you activate it there is a mechanism that forces the shoes to expand against the hub creating friction and slowing you down.



those brake shoes inthe picture expand against the hub. see how when you back pedal or rotate the brake arm that it pushes those shoes against the cone shaped thingy(clutch)? yeah that forces the shoes outwards and to rub the hub.