初中英语河北加拿大版读物04

[07:07.05]5. Take away your hand from under the jar.
[07:14.21]What happens?What is happening?The jar of water is upside down,
[07:20.97]but the water stays in the jar!
[07:25.65]This is because air pressure pushes the cardboard onto the jar.
[07:32.60]There is more air outside the jar than inside,
[07:38.24]so there is more air pressure outside than inside.
[07:45.01]What else can you do?Try the experiment again.
[07:50.96]What happens when you use less water?
[07:56.00]What happens when you use more water?
[08:00.97]What observations can you make?Try it with different kinds and sizes of jars,too.
[08:09.82]Spinning Eggs!
[08:13.06]Jenny:This experiment will teach you three new words:
[08:18.23]"spin,""raw" and "inertia."Brian:"This is an experiment about physics!
[08:25.68]How can you tell the difference between a raw egg and a cooked egg?
[08:32.76]Well,you can break the eggs open.The raw egg is liquid,like water.
[08:40.62]The cooked egg is solid.Is there a way to tell without breaking the eggs?
[08:48.38]Yes!Try this!What do you need?
[08:54.44]two plates two eggs(one raw,one cooked)a pencil a piece of paperWhat do you do?
[09:07.40]1.Spin an eggon each of the plate.What do you observe?
[09:14.55]2.One egg stops first.Which egg?Write down your observation.
[09:23.02]3.Spin both eggs again,
[09:28.19]then quickly stop them from spinning and quickly let go of them again.
[09:34.72]What happens?What is happening?
[09:39.97]When something is still,it does not want to move.
[09:45.25]When something is moving,it does not want to stop.This is called inertia.
[09:52.61](The word inertia comes from the Latin word for "lazy.
[09:59.09]"What was happening with the spinning eggs?
[10:03.35]A raw egg is liquid inside.A cooked egg is solid inside.
[10:10.80]A raw egg has more inertia.This slows it down.
[10:17.77]This is why the raw egg stopped spinning before the cooked egg.
[10:24.12]Which egg started to move when you stopped the eggs and let them go again?
[10:30.67]Yes,it was the raw egg.The raw egg has more inertia.
[10:37.44]The liquid in the raw egg was still moving after you stopped the egg.
[10:44.41]This started the egg spinning again.
[10:48.86]Surprise Your Friends!To:Li-Ming@net.cn
[10:57.92]Subject: An Experiment!From:danny@intersaurus.com
[11:07.59]Date:24/04 5:57 PMHi,Li Ming!
[11:16.65]Do you want to surprise your friends?
[11:20.91]Brian,Jenny and I did an experiment in science class today.
[11:27.78]You can do it,too!First,you need to get ready.
[11:34.23]Get a glass full of water and a piece of cardboard.
[11:40.11]Tell a friend to sit down.Cover the glass with the cardboard,
[11:47.68]and turn the glass over.Hold it over your friend's head.
[11:54.34]Tell your friend,"I am going to take my hand off the cardboard.
[12:00.69]Will the cardboard hold the water in the glass?""No,I don't think so,
[12:08.63]"your friend will say."Keep your hand on the cardboard,please!
[12:15.71]"Next,take your hand off.The cardboard will hold the water up!
[12:23.47]Air is heavier than we think!It pushes down on us from above.
[12:30.63]It also pushes up on us from below.
[12:35.88]In the experiment,air pushes up on the cardboard.
[12:41.52]But it can't push down on the water because the water is inside the glass.
[12:48.47]The air holds the water!Science is interesting.
[12:55.03]Don't you think so?Your friend,Danny
[13:01.40]Did you try this experiment?