science wb ans ch9 ~

點解冇得插入附件既?__________?

9.3 Force of Gravity
Concept checking
1-8 F F T F T F T F
Fill in the blanks
1. weight
2. Newton balance
3. newton
4. kilograms, grams
5. matter


9.4 A space journey
Concept checking
1-7 T F F F T T F

Fill in the blanks
A. The launch
(a) reaction (b) Fuels (c) downward (d) equal
(e) reaction (f) rocket (g) gravity

B. Travel in space
(h) weightlessness (i) gravity (j) friction

C. Return to Earth
(k) high (l) surface (m) air/atmosphere
(n) heat (o) heat-resistant materials

Questions
3. (1) Fill the balloons with more air.
(2) Add a lubricant along the string
(3) Reduce the weight of the balloon rocket
(4) Fix a paper cone on the front part of the balloon.

9.5+9.6 The Life of an Astronaut in Space + Space Exploration
1-6 F F T T T F

Questions
1. (i) strong ultraviolet radiation from the Sun
(ii) extremely high or low temperature
(iii) extremely low gas pressure
2. (i) Both of them are made of poor conductors of heat. This reduces heat gain or loss by conduction.
(ii) Both of them have shiny surfaces to reflect heat radiation. This reduces heat gain or loss by radiation.
3. scratch-resistance lenses, joysticks and specially designed ski boots.
4. Advantages: (i) It is helpful in the development of new materials and technologies.
(ii) It increases our knowledge of the universe.


Disadvantages: (i) It wastes time and money.
(ii) Failures of space exploration programmes may cause death and loss of expensive equipment.
(iii) New technologies may be used in wars.

Part B Integrated Exercise
1-5 T F T T T 6-10 T T F T F 11-13 F T F T F

Multiple Choice
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
D C B B C D D A B D C C C D D C B D

Questions
1. (a) 2 kg (b) mass on Moon = 2 kg, weight on moon = 20/6 =3.33 N
2. The Moon has no atmosphere. No heat is produced due to friction when the space shuttle lands on the Moon.
4. (a) 7 x 500 = 3500 N
(b) 6 x 500 = 3000 N
(c) from 3000 N to 3500 N
(d) Add a lubricant between the block and the table surface.
5. (a) There are many small holes on the surface of the table. Air is pumped out from them and a cushion of air is formed. This reduces the friction between the table and the moving puck.
(b) Use a smooth table without holes. Put some oil/detergent onto the surface of the table to reduce friction. / Add ball-bearings at the bottom of the puck to make it roll smoothly.
6. (b) magnetic force and force of gravity.
(c) (i) to (vi) (ii) to (iv) (iii) to (v)

i don't know but thank you very very much!!!

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