How is it possible that in new moon movie, bella slaps paul across the face and nothing happens to her hand, but in eclipse book when she punches jacob in the face ,her hand breaks?

I thought about that myself. You see, if she just slaps Paul, her hand on flatened and there isn't as much force behind it. Men purposefully turn there heads to the side when they're slapped, anyway, in Eclipse when she punches Jacob, her hand is in a fist and puts forth much more force because she knows it has to take a lot to hurt him. That's why her hand broke.

that is rlly hard to think of because you would think that she would kill her hand but she doesnt... We will prolly always be wondering why her hand didnt break....

i've been repeating that scene a hundred times on youtube, i think she did not slap paul, she kind of punch him on that part. The question as to why she didn't broke a knuckle is perhaps the intensity of anger she felt at that time. She was more angry in eclipse when she was trying to punch Jacob because of the kiss, she was giving more force on the punch for Jacob. That I think is the main reason why she broke her hand.