INTERACTIVE SCIENCE 2B - Www2.hkedcity.net

Workbook Solutions (Enrichment Edn.)
INTERACTIVE SCIENCE 2B
Workbook Solutions (Enrichment Edition)
Chapter 9
SPACE TRAVEL
Part A
Sectional Exercise
9.1
Concept checking p.1
1. True
2. False
3. True
4. False
5. True
6. False
7. True
8. False
Question p.1
C

Workbook Solutions (Enrichment Edn.)
Question p.4
1. (a) (i) slide (ii) trousers of the child
hindrance / reduced / Wear trousers made of a smoother material.
(b) (i) shoes (ii) track/road
help / increased / Wear shoes with more grooves at the bottom / soles.
(c) (i) wedge (ii) floor/door
help / increased / Use a heavier wedge or a wedge with more grooves at the bottom.
2. game: air hockey (or other reasonable answers)
sport: ice-skating, skiing (or other reasonable answers)
9.3
Concept checking p.5
1. False
2. False
3. True
4. False
5. True
6. False
7. True
8. False
Fill in the blanks p.5
1. (a) Magnetic (b) force of gravity
2. downloads
3. (a) force (b) newton
4. (a) 15 (b) 150
5. matter
9.4
Concept checking p.6
1. True
2. False
3. False
4. False
5. True
6. False
7. True
8. False
Fill in the blanks p.6
(a) reaction
(b) Fuels
(c) downwards
(d) equal
(e) reaction
(f) rocket
(g) gravity
(h) weightlessness
(i) gravity
9.2

Workbook Solutions (Enrichment Edn.)
(j) friction
(k) high
(l) friction
(m) air/atmosphere
(n) heat
(o) heat-resistant
Questions p.8
1. (a)
(b)
(c)
(d)
9.3

Workbook Solutions (Enrichment Edn.)
2. (a)
(b) The boy will move towards the wall.
3. (i) Fill the balloon with more air.
(ii) Add a lubricant along the string.
(iii) Reduce the weight of the balloon rocket.
(iv) Fix a paper cone on the front part of the balloon.
(any two answers)
9.5
Concept checking p.9
1. False
2. False
3. True
4. True
5. True
6. False
Questions p.10
1. (i) strong ultraviolet radiation from the Sun
(ii) extremely high or low temperature
(iii) extremely low gas pressure (or other reasonable answers)
2. (i) Both of them are made of poor conductors of heat. This reduces heat entering or
leaving the by conduction.
(ii) Both of them have shiny surfaces to reflect heat radiation. This reduces heat
entering or leaving them by radiation. (or other reasonable answers)
9.4

Workbook Solutions (Enrichment Edn.)
3. • scratch-resistant lenses
• joysticks
• specially-designed ski boots
(or other reasonable answers, ref. to http://www.seds.org/technology.spinoffs.shtml)
4. Advantages: (i) It is helpful in the development of new materials and technologies.
(ii) It increases our knowledge of the universe.
(iii) Ordinary people may travel in space in the future.
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.
(or other reasonable answers)
Part B Integrated Exercise
Concept checking p.11
1. True
9. False
2. True
10. False
3. True
11. False
4. False
12. False
5. False
13. True
6. True
14. False
7. True
15. True
8. True
Multiple choice p.11
1. D
10. D
2. C
11. C
3. B
12. C
4. B
13. C
5. C
14. D
6. D
15. D
7. D
16. C
8. A
17. B
9. B
18. D
Questions p.16
1. (a) 2 kg
(b) Mass on the Moon = 2 kg
Weight on the Moon = 20 N/6 = 3.33 N
2. The Moon has no atmosphere surrounding it. No heat is produced due to friction when
the space module lands on the Moon.
3.
9.5

Workbook Solutions (Enrichment Edn.)
4. (a) 7 2 N = 14 N
(b) 6
5. (a) There are many small holes on the surface of the table. Air is pumped out from
these holes and a cushion of air is formed. This reduces the friction between the
table and the puck.
(b) Use a smooth table (or plastic 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. (or other reasonable answers)
6. (a)
(b) Magnetic force and force of gravity
(c) (i) --- (vi)
9.6

Workbook Solutions (Enrichment Edn.)
7. (a)
(ii) --- (iv)
(iii) --- (v)
Letter
representing
the force
A
D
B
E
F
Description of the force
friction exerting on the trolley by the ground
friction exerting on the boy by the ground
pulling force exerting on the trolley by the boy
friction exerting on the ground by the trolley
friction exerting on the ground by the boy
C reaction force exerting on the boy by the trolley
(b) Forces A and E are equal in size because they are a pair of action and reaction
forces. They are acting in opposite directions.
(c) When force B is greater than force A, the trolley will start moving.
(d) • Force A and force E
• Force B and force C
• Force D and force F
8. (i) When Stephen is on the surface of a planet, his weight will not be zero. His weight
may be more than or less than that on the Earth. It depends on the amount of force
of gravity of the planet.
(ii) The foods for astronauts are completely different from those on the Earth. They are
not as delicious as those he normally eats.
(iii) After living in a weightless environment for a period of time, the muscles of
astronauts will relax. When they return to the Earth, they may not even be able to
stand up due to the force of gravity of the Earth. So, astronauts have to keep doing
physical exercise on a daily basis to maintain their muscles in good condition.
Part C Concept Map p.22
1. start
9. heat
2. direction
10. space
3. shape
11. lubricant
4. action, reaction
12. ball
5. equal
13. non-contact forces
6. opposite
14. mass
7. friction
15. weight
8. motion
Part D Reading Comprehension p.25
(a) The force of gravity of the Earth
(b) • Used rocket stages
• Abandoned satellites
• Unwanted spacecraft parts
• Solid fuel debris
• Debris formed after collisions
9.7

Workbook Solutions (Enrichment Edn.)
(c) A pea-sized piece of debris may penetrate a spacecraft. If this happens on a critical
component, such as the flight computer or fuel tank, it could be fatal.
(or other reasonable answers)
(d) If they fall back to the Earth, most of them will burn completely within the atmosphere.
Few of them will pass through the atmosphere. Those that do are likely to fall into the
sea or places of very low population. So the chance of being hit is extremely low.
(e) (i) Use a space shuttle instead of a spacecraft to reduce the use of rocket stages (used
rocket stages are one of the main parts of space junk).
(ii) Do not launch rockets or space shuttles into space until the technology is well
developed. (or other reasonable answers)
Part E Little Einstein’s Corner p.26
(a) (i) Friction and air resistance
(ii) There is no contact between the train and the guideway, so friction is minimised. In
addition, the train has a streamlined design to minimise air friction.
(b) Non-contact force
(c) (i) Because the train floats along the guideway without contact, there is no need for
any wheels. As a result, maintenance of moving parts is not necessary and the rails
need little maintenance.
(ii) Since maglev trains float, there is no friction. The trains can travel at very high
speed.
(iii) Since maglev trains float, no wheels are rolling along the rails and hence little
noise is produced. (or other reasonable answers)
(d) No. Hong Kong is a small city and the journeys are of short distances. Maglev trains
would have to slow down and stop at a station before a high speed is reached. (or other
reasonable answers)
9.8