F2 IS 2nd Term SE 02 Answers

Concept checking (56 marks)

Decide whether the following statements are true or false, and try to rewrite the true statements.

1.      Non-contact force can only exist between objects that are not in contact.                      True / False

2.      Magnetic force and the force of gravity are examples of non-contact forces.                 True / False

3.      The mass of an astronaut on the moon is less than that on the Earth.                              True / False

The mass of an astronaut on the moon is the same as that on the Earth.

4.      A force is always needed to keep an object moving.                                                        True / False

A force may not be needed to keep an object moving.

5.      When there is no force acting on a moving object, it will eventually stop.                      True / False

When there is no force acting on a moving object, it will not stop.

6.      Friction only acts on a moving object.                                                                              True / False

Friction not only acts on a moving object.

7.      A hovercraft uses water to reduce friction.                                                                      True / False

A hovercraft uses air cushion to reduce friction.

8.      Action and reaction always act in opposite directions.                                                    True / False

9.      Action and reaction always have the same size.                                                               True / False

10.  A rocket produces an upward pushing force by ejecting hot gases downward.              True / False

11.  When we ride on the ‘Abyss Turbo Drop’, the force of gravity acting on us is zero at a certain moment.                                                                                                                        True / False

When we ride on the ‘Abyss Turbo Drop’, the force of gravity acting on us is the same at any movement.

12.  A parachute cannot work in a vacuum.                                                                             True / False

13.  The unit of force can be Newton or kilogram.                                                                  True / False

The unit of force is Newton.

14.  A force can start or stop a motion.                                                                                    True / False

15.  A force can change the speed of an object.                                                                      True / False

16.  Force exists between two objects only when they are in contact.                                    True / False

Force exists between two objects when they are in contact or not in contact.

17.  Weight is a force.                                                                                                              True / False

18.  To start the upward motion of an object, the upward push must be larger than the object’s weight.                                                                                                                                        True / False

19.  The weight of an object is measured in kilogram.                                                            True / False

The weight of an object is measured in Newton.

20.  Friction is useless in our daily lives.                                                                                  True / False

Friction is useful in our daily lives.

21.  An object has the same mass on the Earth and on the Moon.                                          True / False

22.  There is no gravity on the Moon.                                                                                      True / False

There is gravity on the Moon.

23.  A streamlined design can reduce air friction.                                                                   True / False

24.  The grooves in a tyre can prevent a car from slipping.                                                     True / False

25.  A stream-lined design can reduce air friction.                                                                  True / False

26.  Forces always occur in pairs.                                                                                            True / False

27.  The rocket engines must always be on in space travel.                                                     True / False

The rocket engines may not be on in space travel.

28.  A rocket can move around the Earth with its engine off.                                                 True / False

Sentence rearranging (5 marks)

Rewrite the sentence with the following words in correct sequence.

1.      can   /   A force   /   of   /   object   /   an   /   change   /   the speed

A force can change the speed of an object.

2.      can be   /   Forces   /   a spring balance   /   measured   /   by

Forces can be measured by a spring balance.

3.      is   /   measured   /   Weight   /   newtons   /   in

Weight is measured in Newon.

4.      lubricants   /   can be   /   such as   /   Friction   /   oil   /   reduced   /   by

Friction can be reduced by lubricant such as oil.

5.      action   /   always   /   Forces   /   pair   /   reaction   /   occur in   /   and

Action and reaction always occur in pair 

F2 IS 2nd Term SE 01 Answers

M.C.
D, D, D, B, A

Short Question

(a)    Initially, the spring increases in length when the mass of the object is increased.                 (1 M)

        After 40 g, the length of the spring starts to level off and then remains the same even more mass is added.                                                                                                                                  (1 M)

(b)    The numbers on the right column are smaller except the initial length of the spring.            (1 M)

        It is because the force of gravity is smaller on the moon.                                                        (1 M)

F2 IS 2nd Term WS10 Answers

11.1    Senses and sense organs

i      Words to know:

	English term	Write the words again	Chinese term
1	Sense		感覺
2	Detect		探測
3	Stimuli		刺激
4	Respond		反應
5	Sense organ		感覺器官
6	Receptor		感受器
7	Sensitive		敏感
8	Brain		腦
9	Nerve		神經
10	Interpreted		詮釋

i      Fill in the blanks:

1       We have different senses such as sight, hearing, smell, taste and touch.

2       Changes in the environment are called stimuli. Living things can detect and respond to them.

3       By responding to stimuli, living things can find food, mates, shelters and escape from danger.

4       We have different sense organs like eye, ear, tongue, nose and skin. They contain special kinds of cells called receptors which are sensitive to particular kinds of stimuli.

5       When the receptors detect stimuli, they send signals to our brain through nerves, which are then interpreted to give us senses.

i      Fill in the table:

Sense organ	Stimuli	Senses produced
Eye	Light	Sight
Ear	Sounds	Hearing
Nose	Chemicals in air	Smell
Tongue	Chemicals in food or drinks	Taste
Skin	Things in contact with the skin	Heat/cold, touch, pain, pressure

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F2 IS 2nd Term WS09 Answers

10.5    Acid rain

i      Words to know:

	English term	Write the words again	Chinese term
1	Acid rain		酸雨
2	Pollutant		污染物
3	Sulphur / Sulphur dioxide		硫 / 二氧化硫
4	Nitrogen oxides		氮氧化合物
5	Dissolve		溶解
6	Power station		發電廠
7	Fuels		燃料
8	Coal		煤
9	Petroleum		石油
10	Catalytic converter		催化反應器

i      Fill in the blanks:

Acid rain

l  Clean or unpolluted rainwater is slightly acidic with a pH value of about 5.6.

         When the pH value of rainwater drops below 5.6, it is regarded as acid rain.

Causes of acid rain

l  Acid rain is mainly caused by acidic pollutant gases like Sulphur dioxide

and nitrogen oxides. They are released from traditional power station, factories and motor vehicles.

l  The acidic pollutant gases dissolve in tiny water droplets in the air to form acids. The acidic

         water droplets gather together to form clouds, and finally fall as acid rain.

l  The two main sources of acidic pollutant gases are:

(a)        Traditional power stations and factories

Ø  When coals and fuels obtained from petroleum are burnt in traditional power stations and factories, sulphur dioxide and nitrogen oxides are released.

(b)       Motor vehicles

Ø  When fuels are burnt in the engines of motor vehicles, Sulphur dioxide and nitrogen oxides are released.

Environmental effects of acid rain

1           Corroding buildings and structures

l   Acids have corrosive effects on some metals and building materials.

l   Acid rain can gradually corrode building materials and structures made of metal / limestone, marble and limestone / metal.

2           Killing water life

l   Acid rain makes the water in lakes and rivers so acidic that fish and plant cannot survive.

l   Many fish and plants die if the pH value of water drops below 5.

3           Damaging plants

l   Acid rain makes soil too acidic and thus affects plant growth.

l   Acid rain also damage leaves and make plants unable to carry out photosynthesis.

Preventive measures against acid rain

l  Some major ways to reduce the emission (排放) of Sulphur dioxide and nitrogen oxides:

Ø   saving energy so that less coals and fuels obtained from petroleum are burnt;

Ø   using alternative energy sources like solar / nuclear / water power and wind power;

Ø   using high-grade fuels with a low sulphur content;

Ø   reducing pollutants from the exhaust gas of motor vehicles by using catalytic converter.

i      Concept checking:

Decide whether the following statements are true or not and try to rewrite the correct statements.

1.       Unpolluted rainwater is neutral.                                                                                                                       True / False

Unpolluted rainwater is slightly acidic

2.       Rainwater with a pH value below 7 is regarded as acid rain.                                         True / False

Rainwater with a pH value lower than 5.6 is regarded as acid rain.

3.       Carbon dioxide is the major gas that causes acid rain.                                                   True / False

Sulphur dioxide and nitrogen oxides are the major gases that cause acid rain.

4.       The main sources of pollutant gases that cause acid rain are traditional power stations,     True / False

factories and motor vehicles.                                                                                  

5.       Solar power, wind power and nuclear power are alternative energy sources which can  reduce the emission of acidic pollutant gases.                                                                                   True / False