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force n. 力量 v. 迫使；强迫
pressure n.压力，压强；挤压
conclude v. 得出结论；断定；推断出
New phrases
turn…upside down 把 ......翻转；倒过来
pour out 涌出
scientific method 科学方法
take…off 把......拿开
Listen and read
Lesson 25: Let’s Do an Experiment!
Danny, Jenny and Brain are in the lab.
Brain: Let’s do an experiment. I fill a jar with water. I cover the top with a piece of cardboard and hold it there. Then I turn the jar upside down and take my hand off the carboard . Can you guess what will happen?
Danny: I think the floor will get wet . We should do this experiment outside , Brian .
Jenny: I think the cardboard will hold the water .
Danny: I don’t think so .
Jenny: You think the water will pour out ,Danny. I think the water will stay in the jar. Let’s test which theory is correct .
Brian: Good idea ,Jenny. That’s called the sicentific method.
Jenny: I am so sure of my theory that Brian can do the experiment over your head and I know you won’t get wet .
Danny：Well ,let’s try it !
Brian: Are you ready, Danny?
Danny: No！Wait ! (He puts on a raincoat and sits down.)Now I think I’m ready.
Jenny: Brian, take your hand off the cardboard .
Danny: No!(Danny closes his eyes tightly, and Brian takes his hand off the cardboard . The water stays in the jar.)
Jenny: See , Danny?
Danny: How is that possible?
Brian: The force of the air keeps the water in the jar. It is strong enough to hold the water.
Danny: Wow!
Brian: So what have we discovered?
Jenny：We have discovered that the air pressure helps the cardboard water in the jar.
Brian: Right. What do you conclude,Danny?