物理与生活总是密切相关，很多有趣的物理实验也可以借助身边的用品进行，以下就是小明利用矿泉水瓶进行的一些小实验：

（1）如图甲所示，矿泉水瓶中装满水后插入吸管甲，用另一吸管乙向吸管甲上方吹气，吸管甲中水面会上升，这是因为____ ．

（2）如图乙所示，在矿泉水瓶上扎两个相同大小的小孔A和B，发现从B孔喷出的水较急，这是因为____ ．

（3）让矿泉水瓶从某一高度自由落下，则矿泉水瓶下落时运动会越来越快，这是因为力能____ （选填“改变”或“维持”）物体的运动状态．

    Helen got up at seven thirty. Her parents and her little twin brothers went travelling in Australia and she had to take care of herself at home. She opened the fridge, but she found only three pieces of bread in it. She decided to have breakfast in the restaurant at the other side of the street. She sat at a table and the waitress came up to her and said, “Can I take your order, Helen?”

    “But you didn't show your menu to me, Miss White,” said the girl.

    “Oh, sorry! I forget it. Here it is.”

    Helen looked at the menu carefully. It was:

bread  $1.5          egg  $ 0.4

pizza  $2.5          cola  $ 0.3

sandwich $1.5        milk  $ 0.6

hamburger $2.5       coffee  $ 0.9

    Helen took out her purse and found there was only 7 dollars in it.

    “Well,” said White.“What about a hamburger, a pizza, two eggs and a glass of cola?”

    “Oh, no,” said the girl. “I'll buy a storybook this afternoon. It's 2 dollars.”

    “I see,” said the waitress. And then she brought the girl a nice breakfast.