Place value

You can use place value to figure out how much each digit in a number is worth. Each place has a value of 10 times the place to its right.

For example, the number 45 has 4 in the tens place, and 5 in the ones place. In other words, 45 has 4 tens and 5 ones.

The number 372 has 3 in the hundreds place, 7 in the tens place, and 2 in the ones place. In other words, it has 3 hundreds, 7 tens, and 2 ones.


位取くらいど使つかえば、そのかずのそれぞれの数字すうじがどれくらいおおきいかがかります。それぞれのくらいは、そのみぎの位の10倍じゅうばいあたいします。

たとえば、45よんじゅうごは、じゅうの位4よんいちの位5です。えると、10じゅう4つよっつ1いち5ついつつです

372さんびゃくななじゅうには、ひゃくの位3さん、十の位が7なな、一の位が2です。言い換えると100ひゃく3つみっつ107つななつ、1が2つふたつです。

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Kofun (Burial mounds)

Kofun are ancient burial mounds for early emperors and members of powerful clans. They were built from the second half of the 3rd century to the 7th century. This era is called the Kofun period.

The most typical kofun are keyhole-shaped mounds. Around the mounds, regardless of their shape, clay figures called haniwa were placed to decorate and protect the mounds. There were many kinds of haniwa, including those of humans, horses, houses and boats.

There are many remains of kofun all over Japan. Particularly, the Goshikizuka Kofun in Hyogo (picture above) and the Daisen Kofun in Osaka are famous.

The Daisen Kofun is one of the largest tombs in the world. It was built in the 5th century. It is 486 meters long and 305 meters wide.

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Seven continents and four major oceans

There are several ways of defining a continent. In most English-speaking countries, it is taught that there are seven continents on the earth.

The seven continents are Asia, Europe, Africa, North America, South America, Australia (Oceania), Antarctica.

The four major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, and the Southern (Antarctic) Ocean.


大陸たいりく(またはしゅう)の定義ていぎ仕方しかたは、いくつかあります。ほとんどの英語えいごはなくにでは、地球上ちきゅうじょうに7つの大陸(州)があるとおしえられています。

7大陸ななたいりく(7大州だいしゅう)は、アジア大陸(州)、ヨーロッパ大陸(州)、アフリカ大陸(アフリカ州)、きたアメリカ大陸(北アメリカ州)、みなみアメリカ大陸(南アメリカ州)、オーストラリア大陸オセアニア州)、南極なんきょく大陸をさします。

4つよっつ大洋たいようは、太平洋たいへいよう大西洋たいせいようインドよう南極海なんきょくかいをさします。

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Six continents and three major oceans

There are several ways of defining a continent. In Japan, it is taught that there are six continents on the earth.

The six continents are Eurasia, Africa, North America, South America, Australia, Antarctica.

The three major oceans are the Pacific Ocean, the Atlantic Ocean, and the Indian Ocean.


大陸たいりく定義ていぎ仕方しかたは、いくつかあります。日本にほんでは、地球上ちきゅうじょう6つむっつの大陸があるとおしえられています。

6大陸ろくたいりくは、ユーラシア大陸アフリカ大陸きたアメリカ大陸みなみアメリカ大陸オーストラリア大陸南極なんきょく大陸をさします。

3大洋さんたいようは、太平洋たいへいよう大西洋たいせいようインドようをさします。

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Three states of matter

All matter can be classified into three states: solid, liquid, and gas.

Solid: A solid has a definite shape and volume.

Liquid: A liquid has a definite volume but takes the shape of a container.

Gas: A gas has no definite shape or volume.

The state of matter changes depending on the temperature. For example, water at a room temperature is a liquid. When it is boiled, it becomes steam (a gas). When it is cooled, it becomes ice (a solid).


すべての物質ぶっしつは、固体こたい液体えきたい気体きたいの3つの状態じょうたい分類ぶんるいされます。

固体:固体は、かたち体積たいせきわりません。

液体:液体は体積は変わりませんが、形は容器ようきの形になります。

気体:気体は、形や体積が変わります。

物質の状態は、温度おんどによって変わります。たとえば、みずは液体です。沸騰ふっとうさせると、水蒸気すいじょうき(気体)になります。やすとこおり(固体)になります。

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Metamorphosis

Butterflies undergo metamorphosis through four stages of development.

  1. Egg: An adult lays eggs on a leaf of a plant.
  2. Larva: An egg hatches into a larva (caterpillar). It eats leaves and sheds its skin several times to become a pupa.
  3. Pupa: The pupa stays still and grows into an adult in a hard shell called a chrysalis.
  4. Adult: The chrysalis splits and the adult emerges.

チョウは4つの成長せいちょう段階だんかいとおして変態へんたいします。

  1. たまご成虫せいちゅうにたまごをうみます。
  2. 幼虫ようちゅうたまごがかえって、幼虫(アオムシ)になります。葉をべ、数回すうかい脱皮だっぴして、さなぎになります。
  3. さなぎ: さなぎはかたからなかでじっととどまり、成虫のからだに成長せいちょうします。
  4. 成虫: さなぎの殻れて、成虫が羽化うかします。
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The human skeleton

There are 206 bones in the human body. They make up the skeleton, which supports and retains the body. It also protects the brain and internal organs.

Some bones are connected to each other at joints. Cartilage covers and protects the end of the bones of joints. The bones are held together by ligaments.


ひとのからだには206本にひゃくろっぽんほねがあります。それらが骨格こっかくをつくっていて、からだをささえたり、かたちたもったりしています。また、のう内臓ないぞうまもっています。

一部いちぶ関節かんせつでつながっています。なんこつは関節の骨の先端せんたんおおい、ほご護しています。骨はじんたいによってつながっています。

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Magnetism

Magnetism is a force generated by magnets that makes them attract or repel each other.

Magnets have two poles: a north pole and a south pole. When two magnets are placed close to each other, they either attract or repel each other. If the poles are the same, they repel each other. If the poles are opposite, they attract each other.


磁力じりょくは、磁石じしゃくによって発生はっせいする、ったり退しりぞったりするちからです。

磁石にはN極エヌきょくS極エスきょくの2つのきょくがあります。2つの磁石をちかづけると、それらは引き合うか退け合うかどちらかになります。極がおな場合ばあい退け合い、極が反対はんたい場合は引き合います。

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The four forces of flight

There are four forces that act on aircraft: lift, weight, thrust, and drag.

・Lift: a force generated by wings that holds an airplane in the air

・Weight: a force caused by gravity that pulls an airplane down

・Thrust: a force generated by propellers or jet engines that moves an airplane forward

・Drag: a force caused by air friction holding an airplane back.

Lift opposes weight and thrust opposes drag. If lift is greater than weight, the airplane moves upwards. If thrust is greater than drag, the airplane moves forwards. Lift depends on thrust. Therefore, without thrust, the airplane cannot maintain lift.


揚力ようりょく重力じゅうりょく推力すいりょく抗力こうりょくの4つのちから飛行機ひこうき作用さようします。

・揚力:主翼しゅよくによってされる、飛行機を空中くうちゅうかびがらせる力

・重力:重力による、飛行機をろす力

・推力:プロペラやジェットエンジンによって生み出される、飛行機を前進ぜんしんさせる力

・抗力:空気抵抗くうきていこうによってしょうじる、飛行機をもどす力

揚力は重力に対抗たいこうし、推力は抗力に対抗します。揚力のほうが重力よりおおきい場合ばあい、飛行機は上昇じょうしょうします。推力が抗力より大きい場合、飛行機は前進します。揚力は推力に依存いぞんしています。そのため、推力がなければ、飛行機は揚力を維持いじすることができません。

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Airfoil

The cross-sectional shape of an airplane wing is called an airfoil. It is curved, and has a rounded leading edge and a sharp trailing edge. Due to the airfoil, air passes above the wing faster than air passing below. Faster-moving air has a lower pressure than slower-moving air. This difference in pressure generates lift, forcing the wing upward.

The amount of lift changes depending on the angle of attack. The angle of attack refers to the angle between the chord line (imaginary straight line connecting the leading and trailing edges) of the airfoil and the direction of the airflow. As the angle increases, the lift also increases.


飛行機ひこうき主翼しゅよく断面だんめん形状けいじょう翼型よくがたばれます。それは湾曲わんきょくしていて、前縁ぜんえんまるみがあり、後縁こうえんはとがっています。翼型によって、主翼のうえとお空気くうきは、したを通る空気よりもはやながれます。ながれのはやい空気のほうが、流れのおそい空気よりも圧力あつりょくひくくなります。この圧力のから揚力ようりょく発生はっせい、主翼を上へとげます。

揚力のおおきさは、むかかくによってわります。迎え角は、翼型の翼弦線よくげんせん(前縁と後縁を結ぶ想像上の直線)と気流きりゅうきとのあいだ角度かくどのことです。その角度がおおきいほど、揚力もおおきくなります。

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Sensu (Folding fan)

Sensu is a hand-held folding fan. The ribs are made of bamboo or sandalwood, and covered with paper or silk. Since it is foldable, it is easy to carry.

When it is folded up, it looks like a stick. When it is opened, it expands large enough to fan oneself. The shape of sensu is considered auspicious because it broadens out towards the end. This shape is associated with spreading prosperity.

Sensu, like uchiwa, is used to fan oneself to keep cool. However, unlike uchiwa, it is used on formal occasions, such as a tea ceremony. It is also an essential prop used by rakugo performers, and traditional Japanese dancers of noh and kabuki.

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Uchiwa (Fan)

Uchiwa is a traditional Japanese fan. It is round and has a long handle. The frame is made of bamboo or plastic, and covered with paper.

Uchiwa is used for fanning oneself to keep cool in summer. It is used for fanning other things, too. For example, when making sushi, it is useful for cooling and removing the moisture from the rice.

Uchiwa are so commonly used that many businesses use them as an advertisement medium. They distribute uchiwa with their names on them for free in the streets, or at festival venues.

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