根据句意, 用括号内所给单词的适当形式填空。

小题1:Two        (nine)of the students in our school suffer from stress.

小题2:All parents love their children, and my parents love _____________（they）,too.

小题3:The students looked at their teacher _____________ (hope) and were very excited.

小题4:Because of the warm weather children feel______________ (sleep) in class than before.

一个物体质量是2kg，受到两个大小都是10N且互成120°角的力的作用，此外没有其他的力。3s末这个物体的速度是多大？4s内物体发生的位移是多少？