A
What goes up must come down, right? Well, try doing an experiment with a cup of water that stays inside the glass when held upside down. You’ll need the help of some cardboard and a little bit of air pressure.
What you’ll need:
♦ A glass filled right to the top with water
♦ A piece of cardboard
Instructions:
♦ Put the cardboard over the mouth of the glass, making sure that no air bubbles enter the glass as you hold onto the cardboard.
♦ Turn the glass upside down(over a sink or outside until you get good).
♦ Take away your hand holding the cardboard.
What’s happening?
If all goes to the plan, then the cardboard and water should stay put. Even though the cup of water is upside down, the water stays in place, defying gravity! So why is this happening? With no air inside the glass, the air pressure from outside the glass is greater than the pressure of the water inside the glass. The extra air pressure manages to hold the cardboard in place, keeping you dry and your water staying where it should be, inside the glass.
21. What kind of experiment is the passage about?
A. A physics experiment. B. A chemistry experiment.
C. A biology experiment. D. A language experiment.
22. What is the first step to do the experiment?
A. Turn the glass upside down.
B. Take your hand away from the glass.
C. Put the cardboard over the mouth of the glass.
D. Make sure that there are no air bubbles in the glass.
23. What may happen if you take away your hand holding the cardboard?
A. The water pours out of the glass. B. The glass breaks into pieces.
C. The water still stays in the glass. D. The glass has less water.
【答案】21. A 22. C 23. C
【解析】
这是一篇应用文。主要介绍了体验无重力水的实验步骤以及发现，通过实验可以发现：借助纸板和气压的帮助，当杯子倒立的时候，水就会留在玻璃杯里。
【21题详解】
推理判断题。本文是关于“体验无重力水”的实验说明,据常理知,这种实验属于物理实验。故选A。
【22题详解】
细节理解题。根据Instructions部分中“♦ Put the cardboard over the mouth of the glass, making sure that no air bubbles enter the glass as you hold onto the cardboard.( ♦用硬纸板盖住玻璃杯口，按紧硬纸板，确保没有气泡进入玻璃杯)”可知，实验的第一步是把纸板盖在玻璃杯口上。故选C。
【23题详解】
细节理解题。根据What’s happening?部分中“Even though the cup of water is upside down, the water stays in place(即使杯子里的水是倒过来的，水仍然在原地不动)”可知，当你把拿着纸板的手拿开了之后，水仍然留在杯子里。故选C。
