premise: There is a little blond-hair girl with a green sweatshirt and a red shirt playing on a playground. hypothesis: A girl is sitting in a chair.
contradiction: Sentence 1 states a little blond-haired girl while in sentence 2 is only states a girl.  We do not know the girl's size of the girl or her hair color in sentence 2.  In Sentence 1 the girl is playing and in sentence 2 she is sitting which are not the same actions.  In sentence 1 the girl is on a playground and in sentence 2 she is in a chair.  Obviously a chair is not a playground so the two girls  and in entirely different places.