Unit 4
[00:02.98]Look into Science!How Can a Paper Have One Side?
[00:10.63]A piece of paper has two sidess.
[00:15.07]See?This piece of paper has a white side and a pink side.
[00:22.44]In this experiment,In this experiment,we make a piece of paper with one side!
[00:29.07]This experiment teaches you what the word "side" means
[00:35.60]and what the word "edge" means!What do you need?
[00:42.27]a strip of paper markers scissors tapeA strip of paper is a long,
[00:52.22]thin piece of paper.What do you do?
[00:58.38]1.Hold the two ends of the strip of paper together.
[01:05.23]This makes a circle
[01:08.86]2.Turn one end over and tape the two ends together.
[01:15.99]3. Try to colour one side of the strip.
[01:22.76]What happens?
[01:25.92]4.Follow one edge of the strip all around.
[01:32.87]What do you observe?What is happening?
[01:38.82]You have made a Mobius Strip.
[01:42.97]We usually think that a piece of paper has two sides.
[01:48.85]But a Mobius Strip has only one side.
[01:54.00]It also has only one edge.
[01:58.96]It was named after German mathematician August Mobius (1790-1868).
[02:09.62]What else can you do?Cut the strip in half.What do you think will happen?
[02:16.99]Try it and see!
[02:20.36]You can also have fun by making a Mobius Strip big enough to walk in.
[02:26.91]Here's what to do.
[02:30.15]1.Take a very large strip of paper,three to four metres long.
[02:38.09]2. Paint one side or draw pictures on one side.
[02:44.86]3. Hold the two ends of the paper together.
[02:50.89]4. Turn one end over and tape the ends together.
[02:57.53]5. Start walking on the painted side of the strip
[03:04.06]6. Keep walking all the way around.
[03:09.83](You might need a friend to hold the paper up while you walk.)
[03:16.00]Happy Easter!
[03:19.24]Happy Spring!What does Easter celebrate?Easter is a religious festival.
[03:28.67]Christmas is a religious festival,too.Religious festivals are about God.
[03:36.61]Not everyone in Western countries believes in God,
[03:41.96]but most people still like to have a special timewith their families at Easter.
[03:48.62]When is Easter?
[03:51.99]Easter is celebrated in March or April.It is not on the same date every year.
[04:00.35]How did Easter begin?For thousands of years,people have celebrated spring.
[04:07.90]In spring,life returns to the Earth after winter.
[04:10.78]Life "returns" in springbecause plants start to grow again
[04:20.44]andbaby animals are born.Easter celebrates life,too.
[04:27.28]Some people say God's son,Jesus, returned to life on Easter.
[04:33.95]How do families celebrate Easter today?
[04:38.80]Church.Some families go to church on Easter.Easter bunny.
[04:47.35]The Easter bunny is a rabbit.This rabbit is a little like Santa.
[04:53.88]The Easter bunny brings nice surprises for children.Toys?No,not toys.
[05:02.05]Usually the Easter bunny brings candy made of chocolate.
[05:07.51]Easter eggs.Some people paint eggs at Easter -but not the chocolate kind!
[05:14.96]Eggs,spring and Easter go together.Why?
[05:21.23]Because new life comes out of eggs-- baby birds!Special Easter foods.
[05:30.48]At Easter,many people like to have"hot cross buns."A bun is a small bread.
[05:39.02]Hot cross buns have a cross on top.The cross is a symbol of Jesus.
[05:46.59]The cross makes us remember Jesus.
[05:50.96]That's why it's a "symbol.
[05:54.72]"The Force Is All Around You!
[05:58.87]Danny:Oh,no!This is the experiment we're doing for our class!
[06:05.43]Brian:Air pressure is an amazing thing!
[06:09.79]Jenny:Try this experiment over a sink the first time!
[06:14.94]What do you need?
[06:17.97]a glass jar
[06:21.13]a thin piece of cardboard
[06:25.18]Jenny:A book is thick.You want the opposite of thick.1. Fill the glass jar to the top with water.
[06:29.33]You want something thin!Danny:This can't be right!What do you do?
[06:40.88]1. Fill the glass jar to the top with water.
[06:47.04]2. Put the piece of cardboard over the jar.
[06:52.97]3. Turn the glass jar over quickly.
[06:59.00]4.Hold your hand on the cardboard for a few seconds.
[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:[email protected]
[10:57.92]Subject: An Experiment!From:[email protected]
[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?
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