Revision_helper_U9_bilingual.pdf

Part1部分 Revision notes Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 溫習筆記 Chapter Chapter space travel 120 Air and and burning 第 26 章 Forces 力與太空之旅 第 26.2 力的概念 26.2 Concepts about force 力是甚麼？ What is force? Q1 A1
We use a force to push, pull or turn something.

The following figures show some examples of
我們要用力 力才能推、拉或轉動物體。 下圖是日常生活中運用力的一些例子。 forces. We use a force to push the trolley. 我們要用力才能推動手推車。 We need to apply a force to stop the ball. 我們要用力才能抓住足球。 We use a force to hit the ball back. 我們要用力才能把網球打回。 We use a pulling force to open the drawer. 我們要用力才能拉開抽屜。 We use forces to pull the switch. 我們要用力才能拉動風扇的 開關。 We use a force to pull the paper towel. 我們要用力才能把紙巾拉出。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 1 Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 A1 We use a force to turn the doorknob. 我們要用力才能扭開門鎖。 We need to apply a force to twist the towel. 我們要用力才能扭乾毛巾。 We use a force to turn the bottle cap. 我們要用力才能扭開瓶蓋。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 2 if the forces used to push the box below are equal. 箭號的長度表示力的大小。例如，若下圖中推動紙盒的兩個力大小相同，我們應以相 同長度的箭號來表示兩個力。 3.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Q2 In science. the arrows drawn should have equal length. we can use arrows to represent
在科學繪圖中，我們常以箭號來表示力。
下列是以箭號來表示力時要注意的一些 要點。 forces. The arrows points in the direction of the force. The length of the arrow represents the size of force. 箭號的方向必須和力的方向相同。 2. For example. what can we use to represent forces? 在科學表達上，我們常以甚麼來 表示力？ A2
In science. 1.
The following are some tips for drawing arrows to represent forces. 箭號應繪畫在力作用於的物體上。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 3 . The arrow should lie on the object on which the force is acting.
下圖顯示如何利用彈簧秤來 量度拉開抽屜所需的力。 spring balance 彈簧秤 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 4 .
Forces that can act on objects without contact
are non-contact forces.

The following diagram shows a spring balance.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Q3 What are contact and non-contact forces? 甚麼是接觸力和非接觸力？ A3
Forces that exist only between objects in
對物體產生作用的力稱為接觸力 接觸力。 接觸力 contact are called contact forces.

The unit of force is netwon (N).
pointer 指針  indicates the force measured  顯示所量度的力 的大小 scale 刻度
我們可以利用彈簧秤 彈簧秤來量度力 彈簧秤 的大小。 力的單位是牛頓 牛頓 (N)。 下圖顯示彈簧秤。 zero adjuster 零標度校正  use to adjust the position of the scale so that the reading is zero when no force is applied  用來校正彈簧秤，以確保沒有力作用時，彈簧秤的 讀數為零。 hook 掛鈎  for attaching to an object  用來鈎着物件 The figure below shows how to use a spring balance to measure the force needed to open a drawer. Examples include the force of gravity and magnetic force. Q4 只有在物體互相接觸的情況下，才能 在物體沒有互相接觸的情況下，仍能 對物體產生作用的力稱為非接觸力 非接觸力， 非接觸力 磁力和重力 重力是其中兩個例子。 磁力 重力 如何量度力的大小？ What can we use to measure forces? A4
We can use a spring balance to measure forces. Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 A4
We can also use a force sensor connected to
a datalogger to measure forces. computer 電腦 datalogger 數據記錄器 force sensor 力感應器 datalogger 數據記錄器 force sensor 力感應器 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 5 .
The following figures show how to use a force sensor to measure the forces needed to pull a
我們亦可利用連接至數據記錄器的 力感應器來量度力的大小。 力感應器 下圖顯示如何利用力感應器來量度 拉動膠紙座和按動電鈕所需的力。 tape holder and push a button. The force makes the ball start to move. 例如：力能夠令移動中 的足球停下來 Effects of force on objects 力對物體 的影響



Change the direction of motion of an object 改變物體的運動方向 e. 例如：力能夠改變乒乓球 的運動方向



Change the shape of an object 改變物體的形狀 e. 例如：力能夠改變女孩 和單車的運動速率



Stop the motion of a moving object 令移動中的物體停止 運動 e.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Q5 力對物體有甚麼影響？ How do forces affect an object? A5







Cause an object at rest to start moving 令靜止的物體移動 e. The force makes the football stop.g. 例如：力能夠改變檸檬的 形狀 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 6 . The force changes the direction of motion of the ping-pong ball.g.g. 例如：力能夠令靜止的 高爾夫球開始移動 Change the speed of an object 改變物體的運動速率 e. The force changes the shape of the lemon. The force makes the girl and the bicycle move faster.g.g. It can make an
摩擦力是一種接觸力 ，它會令物體保 摩擦力 持靜止不動，或阻礙物體的運動。
例如：當施加在書本上的推力未能克 object stay still. there is also a force 當物體在液體 (如水) 或氣體 (如空 氣) 中移動時，亦會出現一股力阻礙 opposing its motion. 火箭在空氣中以高速 移動時，會遇到很大的 空氣阻力。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 7 .3 摩擦力 26. or oppose the motion of a moving object. Therefore. 當書本在實驗枱上滑動時，書本和實 驗枱之間的摩擦力會阻礙書本的運 動，使書本移動的速率減慢，並最終 停下來。 The book slows down 書本的速率減慢 The book stops 書本停下來 friction 摩擦力
water) or gas (e. when the pushing force cannot 服摩擦力時，書本會保持靜止不動。 overcome the friction between the book and the bench. when we stop pushing. the book slows down and finally stops.g. there is air resistance opposing our motion.3 Friction Q6 甚麼是摩擦力？ What is friction? A6
Friction is a contact force. there is large air resistance acting on it.
resistance. the friction opposes
its motion. This is called fluid 其運動，這股力稱為流體阻力 流體阻力。 流體阻力 When an object moves through a liquid (e.g. When we ride a bicycle. the book stays still.
For example. 例如： For example. pushing force 推力 The book does not move 書本保持靜止不動 friction 摩擦力
When the book is moving. 我們踏單車時，會感受到 空氣阻力。 When a rocket moves at a high speed. air).Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 26. 慢慢增加拉力直至木塊開始移動。彈簧秤的讀數便是木塊和實驗枱之間的 摩擦力。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 8 .Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Q7 如何量度摩擦力？ What can we use to measure friction? A7
We can use a spring balance to measure friction. pull 拉 Slowly increase the pulling force until it is just large enough to make the block move.
我們可利用彈簧秤來量度摩擦力。
The following figure shows how to use a spring
下圖顯示如何利用彈簧秤量度木 balance to measure the friction between the 塊和實驗枱之間的摩擦力。 wooden block and the bench. The reading of the spring balance shows the friction between the wooden block and the bench. This helps them run more smoothly and can also reduce wear. 1.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 In some situations. 利用潤滑劑或空氣把接觸面分隔  The friction between two surfaces can be  潤滑劑或氣墊均能把兩個接觸面分隔， reduced by separating them with lubricant or a 使接觸面之間的摩擦力大大減少。 layer of air. friction or fluid 摩擦力或流體阻力有時會在生 resistance may cause problems. 氣墊船裝有強大風扇，能把空氣從船底吹出，形 成一層氣墊，大大減少摩擦力，令船可在水面快 速航行，甚至在陸地上行駛。 Lubricant can be used to reduce friction between moving machine parts. Friction is greatly reduced and therefore the hovercraft can move smoothly over the water. How can 活中造成不便。有甚麼方法可 we reduce friction or fluid resistance? 減少摩擦力和流體阻力？ Q8 A8
Scientists have found several ways to reduce friction or fluid resistance.  The following are some examples of reducing  以下是一些利用氣墊或潤滑劑來減少摩 friction by separating surfaces. Separating surfaces with a lubricant or air
科學家發展出不少減少摩擦力和流體阻 力的方法。 1. a large fan is used to blow air downwards to form an air cushion beneath the hovercraft. 潤滑劑能減少單車活動部分之間的摩擦 力，這可使活動部分運轉得更暢順，並能 減少磨損。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 9 . 擦力的例子。 fan 風扇 air cushion 氣墊 In a hovercraft. 滾筒可應用於輸送帶，使包裹能在輸送帶 上暢順地滑行。 Bearings are used in bicycles so that the wheels can rotate smoothly. Airplanes and trains have a streamlined shape to reduce air resistance. 身體亦呈流線型，以減少在水中活動時 Many organisms in water also have a 3. 飛機和火車的流線型設計能減少它們移 動時所遇到的空氣阻力。 3. bearing 滾珠軸承 rollers 滾筒 Rollers are used to reduce friction so that the box can slide smoothly and quickly. 2. 把物體的運動方式由滑動變成滾動  The friction between two surfaces can be  利用滾筒或滾珠軸承可以把物體的運動 方式由滑動 滑動變成滾動 滾動，以減少物體接觸 滑動 滾動 reduced by using rollers or bearings. 旗魚的身體呈流線型，可以減少牠在水中游泳 時遇到的阻力，因此牠們能以高速在水中游泳。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 10 . the  物體在液體和空氣中移動時會遇到阻 力。若物體的形狀呈流線型 流線型，所遇到的 流線型 fluid resistance acting on it is smaller if the 阻力會較小。 object has a streamlined shape. trains and airplanes usually have a  汽車、火車和飛機一般都會設計成流線 型，以減少空氣阻力。不少水生生物的 streamlined shape to reduce air resistance. They can 面之間的摩擦力。在日常生活中，滾珠 change sliding motion to rolling motion.  Cars. 滾珠軸承可應用於單車，使輪子轉動得更暢順。 流線型  When an object moves in a liquid or a gas. Designing the object with a streamlined shape streamlined body to reduce resistance in water.  The following are some examples.  The following are some examples of using  以下是利用滾筒或滾珠軸承來減少摩擦 力的例子。 rollers or bearings to reduce friction. 所遇到的阻力。  以下是一些例子。 A sailfish has a highly streamlined body to reduce resistance in water. Changing sliding motion to rolling motion 軸承常被應用於機器內以減少摩擦力。 They are commonly used in machines to reduce friction. It can swim quickly in water.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 A8 2. 制動器與單車車輛之間的摩擦力 有助減慢車輛的速率。
我們在日常生活中經常會應用到摩擦力， 以下是一些例子。 防止滑倒 Some staircases are covered with a rough material to prevent slipping. Prevent slipping or skidding The friction between the rubber sheet and our feet prevents us from slipping in a bathtub. 有些階梯鋪有一條粗糙的防滑物 料，以防止行人滑倒。 固定物體的位置 The friction between the nail and the wood holds the nail in position.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Q9 Friction is important to our daily lives. 作用在降落傘的空氣阻力有助減慢跳 傘員下墜的速率，使他能安全着陸。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 11 . 衣夾和襪子之間的摩擦力能固定襪子的 位置。 Slow down a moving object The friction between the brake and the wheel rim slows down the wheel of the bicycle. What are the common uses of friction? 用摩擦力？ A9
摩擦力對我們十分重要， 我們在日常生活中如何應 We often make use of friction in daily life. 在浴缸鋪上防滑膠墊，可增加摩擦 力，防止我們在浴缸內滑倒。 Hold an object in position The friction between the clothes clip and the socks holds the socks in position. The following are some examples. 鐵釘和木板之間的摩擦力能固定鐵釘 的位置。 減慢物體的運動速率 The air resistance acting on the parachute slows the skydiver down and helps him land safely. Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 A9 Move objects The friction between our shoes and the ground enables us to walk. 摩擦雙手時會產生熱，令我們雙 手感到溫暖。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 12 . 筷子與食物之間的摩擦力令我們 能把食物夾起。 產生熱 We can produce heat by rubbing our hands. 鞋底與路面之間的摩擦力令我們 能夠步行。 Produce heat The friction between the box and the match produces heat that makes the match ignite. 火柴盒與火柴之間的摩擦力可產 生熱，令火柴燃點起來。 移動物體 The friction between the chopsticks and the food allows us to pick up the food. 4 重力 26.4 The force of gravity Q10 甚麼是重力？ What is the force of gravity? A10
The force of gravity exerted by the Earth pulls
在地球表面及地球周圍的物體，都受
到地球的重力 重力所吸引，這重力指向地 重力 球的中心。 以下是重力的影響： objects towards the centre of the Earth. It
重力是一種非接觸力，物體不需要和 can act on an object at a distance. 重力把我們吸附在地球的表面。 It causes objects to fall. 重力使物體跌回地面。 It pulls down objects we throw into the sky.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 26. 太空船受到地球重力所吸引。 It keeps us on the Earth’s surface. 重力會隨距離增加而減少。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 13 . 重力把我們拋向空中的物體拉回地面。
The force of gravity is a non-contact force.
The effects of the force of gravity are shown below: It tends to pull a spacecraft back to the Earth. It decreases 地球接觸，亦會受地球的重力吸引。 when distance increases. Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 14 . It is measured in newtons.
The mass of an object is constant. 這個筆袋的重量是 3 N，這表示地球施加在這個筆袋 的重力為 3 N 。 Q12 What are the differences between mass 質量和重量之間有甚麼不同？ and weight? A12 Mass 質量 Weight 重量 The amount of matter in an The force of gravity acting on object an object 物體所含物質的多少 施加在物體的重力 kilogram (kg) / gram (g) newton (N) 千克 (kg) / 克 (g) 牛頓 (N) different places? yes no 它在不同的地方是否 保持不變？ 保持不變 ？ 是 不是 What is it? 它是甚麼？ 它是甚麼？ What is its unit? 它的單位是甚麼？ 它的單位是甚麼？ Is it always the same in
The greater the mass of an object. but its weight may change from one place to another.
The weight of this pencil box is 3 N.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Q11 甚麼是物體的重量？ What is weight? A11 The force of gravity exerted by the Earth on an

地球施加在物體的重力稱為重量 重量。 重量
重量是力的一種，單位是牛頓。 object is known as weight. the larger the
物體的質量愈大，地球施加在該物體 的重力亦愈大，因此該物體便愈重。
物體的質量在不同地方都是相同的， 但它的重量卻可能有所不同。 force of gravity is and hence the greater its weight is. Weight is a force. That means the Earth exerts a force of gravity of 3 N on it. and returning to the Earth.
Action and reaction always occur in pairs and
act on different objects.
The following are some examples of action and reaction.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Chapter 第 27 章 A space journey 太空旅程 27. travelling in space. The water also exerts a force on the paddle to push the boat forward.
科學家利用作用力 作用力和反 作用力 反作用力的原 作用力 理把火箭發射上太空。 作用力和反作用力總是成對出現， 並且作用於不同的物體上，它們的 大小相同，但方向卻是相反的。 日常生活中有不少作用力和反作用 力的例子，以下是其中一些例子。 force exerted by the paddle on the water 船槳向水施加的力 force exerted by the water on the paddle 水向船槳施加的力 The paddle exerts a force on the water.2 發射升空 27. 圖中的男孩划水時，船槳向 水施力，水亦同時向船槳施 力，令船前進。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 15 .2 Launching What is the working principle of Q14 火箭發射時應用了甚麼原理？ rockets? A14
Rockets work on a principle of action and
reaction. 27. They have the same size but act in opposite directions.1 Stages of a space journey 27.1 太空旅程的各個階段 太空旅程主要分為哪三個 階段？ What are the three stages of a space Q13 mission? A13 太空旅程主要分為三個階段：「發射升 空」、「在太空中航行」、「重返地球」。 A space mission consists of three stages: launching. 當汽車 A 撞向汽車 B 時， 汽車 A 向汽車 B 施力，令 汽車 B 損毀。同時汽車 B 也向汽車 A 施加方向相反 的力，令汽車 A 損毀。 principle of action and reaction to 究竟科學家怎樣把作用力和 反作用力的原理應用到火箭 launch a rocket? 發射之上？ How do scientists make use of the A15
Scientists apply the principle of action and
科學家利用作用力和反作用力的原 理來產生力，以推動火箭前進。
火箭內載有大量燃料，燃料燃燒時 會產生大量熾熱的氣體，當火箭把 這些熾熱氣體向下噴出時，氣體亦 reaction to produce the force that pushes the rocket into space. the gases exert an opposite force to push the rocket upwards.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 A14 car A 汽車 A car B 汽車 B force exerted by car B on car A 汽車 B 向汽車 A 施加的力 Q15 force exerted by car A on car B 汽車 A 向汽車 B 施加的力 When car A hits car B. 同時向火箭施以方向相反的力，令 火箭向上升。 force exerted by the gases on the rocket 氣體施加在火箭上的力 force exerted by the rocket on the gases 火箭施加在氣體上的力 Action and reaction involved in rocket launch 發射火箭時所涉及的作用力 和反作用力 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 16 . the force exerted by car A causes car B to collapse. Car B also exerts an opposite force which makes car A collapse.
Inside a space rocket. the fuel burns and produces a large amount of hot gases. When these gases are ejected downward. we can test for hydrogen using the burning splint test.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Q16 What are the difficulties in launching 火箭發射升空時會遇到甚麼 rockets into space? How are the 困難？火箭的哪些設計有助 解決這些困難？ rockets designed to overcome these difficulties? A16 Difficulties in launching rockets How are the rockets designed to into space overcome these difficulties? 火箭發射升空時會遇到的困難 火箭的哪些設計有助解決這些困難？ 火箭的哪些設計有助解決這些困難？ 1.
In the laboratory. Each stage is dropped off once the fuel is used up so as to reduce the weight of the rocket 2. a ‘pop’ sound is heard. 火箭需要達至極高速
Use rocket boosters to provide extra pushing force to the rockets
使用助推火箭 助推火箭，在升空初期為火箭提供 助推火箭 額外的推進力 3. The rocket needs to reach a very high
speed 採用多節式 多節式設計，當一節火箭的燃料耗 多節式 盡後，該節火箭便會脫離，以減輕火箭 的重量 2.
When a burning splint is put into a test tube containing hydrogen. There is large air resistance which may Have a streamlined shape to reduce air slow down the rocket resistance 3. 太空中沒有燃燒燃料所需的空氣 載有液體氧
Use a multi-stage design.
Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 17 . 火箭高速移動時，會遇到很大的空氣阻 設計成流線型，以減少火箭高速移動時所 力，會減慢火箭的速率 Q17 Which gas is commonly used as 火箭常以甚麼氣體為燃料？ rocket fuel? How can we test for it in 在實驗室內，我們如何測試這氣 體？ the laboratory? A17
遇到的空氣阻力 Hydrogen is commonly used as a rocket fuel. No air in space for the rocket fuel to burn Carry its own oxygen supply to burn the fuel 1. only water vapour is formed.
氫常被用作火箭的燃料，它燃燒時 只會產生水蒸氣。
在實驗室內，我們可利用燃燒中的 木條來測試氫。 當我們把燃燒中的木條放入盛有氫 的試管時，會聽到「卜」一聲。 When it burns in air. we can slide over a long distance on the ice.
The following is an example of weightlessness we can experience.
太空船環繞地球航行時，太空人以及 其他物體可以在太空船內「飄浮」， 好像沒有重量一樣，這樣的狀態稱為 無重狀態。 無重狀態
我們可感受到無重狀態的例子： astronauts and other objects inside the spacecraft can ‘float’ around. Therefore. This kind of motion is called frictionless motion. In skating. It seems that they have no weight. As the roller coaster train starts to move down from the top of the steepest rides.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 27. 當過山車從陡斜軌道的最高處往下衝時，你會經 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) 歷到短暫的無重狀態。 © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 18 . there is no air resistance to slow a
太空中沒有空氣，因此不會有空氣阻 力減慢太空船的航行速率，即使關掉 火箭引擎，太空船仍能繼續向前移 動，這種運動稱為無摩擦運動 無摩擦運動。 無摩擦運動
以下是一個類似無摩擦運動的例子： spacecraft down. They are in a state of weightlessness.3 在太空中航行 27. 溜冰鞋和冰面之間的摩擦力很小，因此溜冰時我 們可以滑行一段頗長的距離。 Q19 甚麼是無重狀態？ What is weightlessness? A19
When a spacecraft travels round the Earth. Therefore.3 Travelling in space Q18 How does a spacecraft move in space? 太空船如何在太空中航行？ A18
In space.
The following is an example of ‘frictionless motion’ in daily life. there is little friction between the skates and the ice. you can feel a sense of weightlessness. a spacecraft can keep moving with its engine off. 27. 完成太空任務重返地球後，神舟七號的返回艙會 有一些燒焦的痕跡。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 19 . a large amount of heat is produced.4 重返地球 27.4 Returning to the Earth Q21 What happens when a spacecraft passes 太空船重返地球時會以高速 through the Earth’s atmosphere as it returns 穿越大氣層，在這情況下會 發生甚麼事情？ to the Earth? A21
When a spacecraft passes through the Earth’s
太空船以高速穿越大氣層時，由於船身 和空氣摩擦，因此會產生大量的熱。
要保護太空船船艙內的太空人，太空船 atmosphere at high speed. there are burn marks on the return capsule of Shenzhou 7.
To protect the astronauts inside.
The spacesuit also helps to maintain a suitable temperature for the astronaut. the outer surface of the spacecraft is covered with a heat 的表面必須以隔熱罩 隔熱罩或隔熱磚 隔熱罩 隔熱磚覆蓋。 隔熱磚 shield or insulating tiles.
太空人在太空船外工作時，必須穿上太 太 空衣來保護自己。 空衣
太空衣內能維持於一個適合人體的 溫度，使太空人免受太陽的高溫傷害。 they need to wear a spacesuit to protect themselves against the extreme environment in space.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 How do the astronauts protect themselves Q20 when working outside the spacecraft? 太空人在太空船外工作 時，如何保護自己？ A20
When astronauts work outside the spacecraft. burn marks 燒焦的痕跡 After the space mission.
To ensure a safe landing. Large parachutes are used to slow down a spacecraft. parachutes are open. 太空船利用大型降落傘來減速。 Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 20 .Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Q22 What are used to slow down a spacecraft so that it can land safely? 科學家利用甚麼來減慢太空船下跌 的速率，令它可以安全着陸？ A22
Parachutes are used to slow down the
太空船降落時會利用降落傘來減速。
太空船降落時會張開降落傘，降落傘遇 spacecraft for safe landing. There is large air resistance acting on the parachutes and this helps to slow down the 到的空氣阻力很大，故此能減慢下跌的 速率，令它可以安全着陸。 spacecraft. Oxygen is commonly used as a fuel for rockets. 3. (I) and (II) only B. (I). (II) and (III) □ Which of the following is NOT the effect of friction? A. A. Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 □ 21 . It produces heat. 4. C. Action and reaction always have different size. 7. It speeds up a moving object. Contact forces can act on an object at a distance. A. (III) Forces can change the shapes of objects. (II) Forces can change the directions of motion of objects. In science. Bearings are used in machines to reduce friction. (I) and (II) only B. (I) and (III) only C. 8. Weight can be measured by using a spring balance. (II) and (III) only D. arrows are used to represent forces. □ 2. (I) and (III) only C. 3. (I). B. B. □ □ □ □ 6. It holds an object in position. (II) and (III) □ Which of the following are the effects of forces on objects? (I) Forces can cause objects to move. Which of the following are non-contact forces? (I) Force of gravity (II) Friction (III) Magnetic force 2.Part Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 第 2 A. (II) and (III) only D. Multiple-choice questions 多項選擇題 □ □ □ Choose the correct answer for each of the following questions. Mass is a force. 細閱以下句子，正確的在方格內填上「T」，不正確的則填上「F」。 1. 5. It prevents slipping. D. 選出正確的答案，然後在空格內填上代表該答案的英文字母。 1. The unit of friction is newton (N). 部分 Revision exercise 單元練習 True or false questions 是非題 Write ‘T’ for a true statement or ‘F’ for a false statement in each box provided. (II) and (III) only D. Which of the following statements are correct? (I) The Earth exerts a larger force of gravity on the elephant. (I) and (II) only B. It causes objects to fall. (II) and (III) only D. A. B. Which of the following statements concerning the force of gravity is INCORRECT? A. The weight of the plastic box on the Moon is larger than its weight on the Earth. 7. (I) and (III) only C. (I) and (II) only B. C. □ The mass of a plastic box is 2 kg. 5. It is measured in newtons. The mass of the plastic box on the Moon is smaller than its mass on the Earth. Which of the following statements is correct? A. It decreases when distance decreases. The weight of the plastic box on the Moon is equal to its weight on the Earth. (I). (II) and (III) Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 □ 22 . C. B. 8. (II) They always act on the same objects. (III) They always act in opposite directions. (II) and (III) □ Which of the following statements concerning action and reaction are correct? (I) They always occur in pairs. A. (II) The elephant has a greater weight. (II) and (III) only D. (II) and (III) □ Which of the following statements about weightlessness is INCORRECT? (I) It only occurs in space. they still have weight. 6. (I). D.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 4. D. (I) and (III) only C. □ An elephant has a mass of 150 kg and a rabbit has a mass of 5 kg. (III) When astronauts are in a state of weightlessness. (II) It only occurs when there is no force of gravity acting on objects. (I) and (III) only C. (I) and (II) only B. (I). A. The mass of the plastic box on the Moon is equal to its mass on the Earth. It tends to pull objects towards the centre of the Earth. (III) The masses of the elephant and the rabbit on the moon are 150 kg and 5 kg respectively. (a) ______________________________________________________________________ (b) _____________________________________________________________________ Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 23 . Also. Draw the reaction in each of the following diagrams. (b) Suggest a way to reduce the friction between the cupboard and the floor? ______________________________________________________________________ 2.Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 C. (a) Draw arrows to represent the pushing force and the friction acting on the cupboard. write down the object on which the reaction acts. Short questions 短問題 1. A man is moving a cupboard on the floor. T 6.Part Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 Answers 答案 A. F B. Multiple-choice questions 多項選擇題 1. B 8. (a) pushing force friction acting on the cupboard (b) Some rollers are put between the cupboard and the floor. B 2. T 5. A C. (or any other reasonable answers) Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 24 . D 7. Short questions 短問題 1. F 7. F 2. T 4. B 4. C 5. B 6. F 8. D 3. True or false questions 是非題 1. T 3. (b) The reaction acts on the racquet. (a) The reaction acts on the hand. Understanding Integrated Science for the 21st Century (3rd Edition) 最新綜合科學 — 邁進 21 世紀 (第三版) © Aristo Educational Press Ltd 2012 © 雅集出版社有限公司 2012 25 .Revision Helper 溫習錦囊 (Bilingual version) 雙語版本 2.