F2 IS 2nd Term WS03 9.3 Answers

2nd Term WS 03 Submission date：_____________ Name：______________________ Class & no.：2 _________(     )

9.3       Force of gravity

i     Words to know:

	English term	Write the words again	Chinese term
1	Force of gravity		重力
2	Pull / Pulling		拉
3	Exert (... on…)		施加 (…於…)
4	Centre		中心
5	Celestial bodies		天體
6	Weight		重量
7	Mass		質量
8	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

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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

F2 IS 2nd Term QZ 01 anwers

2nd Term QZ 01 Submission date：_____________ Name：______________________ Class & no.：2 _________(     )

9.1

Word Translation (8 marks)

i    Write down the English terms of the following Chinese terms:

	Chinese term	English term
1	力	Force
2	運動	Motion
3	方向	Direction
4	速度	Speed
5	彈簧秤	Spring balance
6	牛頓	Newton
7	接觸力	Contact force
8	非排觸力	Non-contact force

Multiple Choice (4 marks)

Circle the letter of the best answer for each question.

1.       A force CANNOT change ____________________ .

A.   the speed of motion of an object                   

B.   the shape of an object

C. the mass of an object                                    

D.   the direction of motion of an object

2.       When a volleyball player hits the ball, the applied force changes ____________________ .

A.   the mass of the ball                                

B.   the weight of the ball

C.   the speed of motion of the ball              

D. the speed and the direction of motion the ball

3.     Which of the following statements about forces is/are correct?

(I)   A spring balance is used to measure forces.

(II) A force can change the speed of a moving object.

(III)        A force can make an object move, but it cannot stop a moving object.

A. (I) and (II) only     

B.   (I) and (III) only    

C.   (II) and (III) only   

D.   (I), (II) and (III)

4.       Which of the following statements about a spring balance is correct?

A.   It can be used to measure a contact force, but not a non-contact force.

B.  It can be used to measure friction.

C.   We may get different readings if we measure the same force on different celestial bodies.

D.   If the spring in a spring balance is replaced, the pointer will always point at the  same position when measuring the same force.

Fill in the Blanks (9 marks)

1      A (1) force can start and (2) stop the motion of an object.

2      A force can also change the (3) speed / direction and the (4) direction / speed of motion of an object.

3      (5) Spring balance is an instrument which is used to measure forces. The unit of force is (6) newton and the symbol is (7) N.

4      The forces that act on object through direct contact are known as (8) contact force. The forces that can act on objects without direct contact are called (9) non-contact force.

Challenging Questions (Bonus 2 marks)

1.      Describe one effect of forces seen when a bowling ball hits the pins.

The force starts the motion of the pins / changes the direction or/and the speed of the the motion of the pins.

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2.      When a football player kicks the moving ball, the force changes the direction and the speed of the motion of the ball.

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F2 IS 2nd Term WS02 9.2 Answers

2nd Term WS 02 Submission date：_____________ Name：______________________ Class & no.：2 _________(     )

9.2       Friction

i    Words to know:

	English term	Write the words again	Chinese term
1	Friction		磨擦力
2	Oppose		相反 / 對抗
3	Slide / sliding		滑動
4	Air (or water) resistance		空氣 (或水) 阻力
5	Air cushion		氣墊
6	Lubricant		潤滑劑
7	Rollers		滾子
8	Ball bearings		滾珠軸承
9	Streamlined shapes		流線型

i     Concept checking: Decide whether the following statements are true or false, and try to rewrite the true statements.

1      Friction only causes inconvenience.                                                                               True / False

Friction sometimes causes inconvenience.

2      Oil reduces friction by separating two contacting surfaces.                                         True / False

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i    Multiple choice: Circle the letter of the best answer for each question.

1.      Which of the following properties of an object is NOT affected by a force?

1. Shape
2. Weight
3. Mass
4. Direction of motion

2.      Which of the following is/are NOT example(s) of reducing friction?

(I)                 The air cushion of a hovercraft

(II)               The streamlined shape of a racing car

(III)             Covering a wet floor with a piece of thick cloth

1. (I) only
2. (III) only
3. (I) and (II) only
4. (II) and (III) only

i    Short question

1.      Suggest TWO ways to reduce friction between two contacting surfaces.

Using a air cushion / a lubricant / ball bearings (any TWO)

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2.      Suggest TWO examples from daily life where friction is useful to us.

Friction between our shoes and the ground enables us to walk or run.

Friction between a door knob and our hand enables us to open the door.

(OR other reasonable answers)

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3.      Suggest TWO examples in daily life where friction is increased.

We use a towel to increase friction when trying to open the lid of a bottle.

/ Hiking boots have deep grooves on the sole to increase friction and prevent slipping.

/ The plastic non-slip grip on a ball-pen prevents slipping and makes writing easier.

/ Using a folk or chopstick to pick up food.

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4.      What energy change is involved when two objects are continuously to rubbed against each other?

Kinetic energy is changed into heat energy.