|
9.3 Force
of gravity
i Words to know:
|
|
English term
|
Write the words again
|
Chinese term
|
|
1
|
Force of
gravity
|
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重力
|
|
2
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Pull / Pulling
|
|
拉
|
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3
|
Exert (... on…)
|
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施加 (…於…)
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4
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Centre
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中心
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5
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Celestial
bodies
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天體
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6
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Weight
|
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重量
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7
|
Mass
|
|
質量
|
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8
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Matter
|
|
物質
|
i Skill
development – Writing
1.
The Earth exerts a force of gravity on every object
on or around it. The force pulls the objects towards the centre of the Earth.
2. The Moon exerts a force of
gravity on every object on or around it. The force pulls the objects towards
the centre of the moon.
3. Mars (火星) exerts exerts a force of gravity on every object
on or around it.
The force pulls the
objects towards the centre of mars
i Concept checking: Decide whether the following
statements are true or false, and try to rewrite the true statements.
1 The force of gravity is the same everwhere. True
/ False
The
force of gravity is different everywhere / the mass is the same everywhere.
2 The mass of an object is the force of
gravity acting on it. True
/ False
The
mass of an object is the amounts of matters it contains.
3 The force of gravity is an example of a
non-contact force. True / False
_____________________________________________________________________________
4 When an object is launched into space, its
mass becomes smaller. True / False
When an
object is launched into space, its weight becomes smaller / its mass remains
unchanged.
i Multiple choice: Circle
the letter of the best answer for each question.
1. Which
of the following statements is/are correct?
(I) No
force of gravity acts on an object when it rests on a desk.
(II) An artificial satellite can move around the
Earth even though it has no engine.
(III) Raindrops fall down due to gravity.
A. (I)
only B. (III)
only C. (I)
and (II) only D. (II) and
(III) only
2. Which of the following statements about weight is/are correct?
(I) Weight is a kind of force.
(II) The
weight of an object depends only on the amount of matter the object contains.
(III) An object falls down because of its weight.
A. (I)
only B. (I)
and (II) only C. (I) and
(III) only D. (II)
and (III) only
3. Which of the following statements is/are
correct?
(I) Every object has the same mass on the Earth
and on the Moon.
(II) Every object has different weights on the Earth
and on the Moon respectively.
(III) The
mass of an object is the force of gravity acting on it.
A. (I)
only B. (III)
only C. (I) and
(II) only D. (II)
and (III) only
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