Daniel, Sandy and Simon are in the lab.
Simon: Let's do an experiment. I fill a jar(罐子) with water. I cover the top with a piece of cardboard(纸板) and hold it there. Then I turn the jar upside down and take my hand off the cardboard. Can you guess what will happen?
Daniel: I think the floor will get wet. We should do this experiment outside, Simon.
Sandy: I think the cardboard will hold the water.
Daniel: I don't think so.
Sandy: You think the water will pour out, Daniel. I think the water will stay in the jar. Let's do the experiment to test whose opinion is correct.
Simon: Good idea, Sandy.Thatis called the scientific method.
Sandy: I am so sure of my opinion that Simon can do the experiment over your head and I know you won't get wet.
Daniel: Well, let's try.
Simon: Are you ready, Daniel?
Daniel: No! Wait! (He puts on a raincoat and sits down.) Now I think I'm ready.
Sandy: Simon, take your hand off the cardboard.
Daniel: No!
(Daniel closes his eyes tightly(紧紧地), and Simon takes his hand off the cardboard. The water stays in the jar.)
Sandy: See, Daniel!
Daniel: How is that possible?
Simon: The force(力) of the air keeps the water in the jar. It is strong enough to hold the water.
Daniel: Wow!
Simon: So what have we discovered?
Sandy: We have discovered the air pressure(压力) helps the cardboard hold the water in the jar.
Simon: Right. What do you conclude, Daniel?
Daniel: I conclude that air is stronger than I thought.
