题目

如图7-5-13所示，底面积为2a2的两个圆柱形容器，底部用细管连接，左边容器的水面浮着一个边长为a的正方形木块，木块的一半浸在水中.现将木块慢慢提出水面，则容器中水的重力势能减少了. 图7-5-13 答案：解析：可用等效法解.提出木块，设想水不流动，仅左边水面达到水平，重力势能减少.然后水流动，左右两边水面达到水平，重力势能又减少，故重力势能共减少.答案：句型转换(每小题2分,共10分)按照要求完成下列句子,每空一词。1.My family name is Clark. (对画线部分提问)______ ______ family name?2.Tina likes pears. (改为一般疑问句)______ Tina ______ pears?3.Bill has an English dictionary. (改为否定句)Bill ______ ______ an English dictionary.4.Those are oranges. (改为单数句)______ ______ ______ orange.5.Tom has many balls. (改为同义句)Tom has ______ ______ ______.