1. ASSIGNMENT BOOK Unit 9 Part 1 9.5 A. Check your concepts Study the following statements. Put a ‘ T ’ in the box against a correct statement and a ‘F’ against an incorrect statement. F T 1.Action and reaction always occur in pairs. 9.5A Space Journey 2.In some cases, reaction may be greater than action. 3.Jet engines cannot be used in space because they need air to burn the fuel. T

2. ASSIGNMENT BOOK Unit 9 Part 1 9.5 T T F F 7. When a spacecraft passes through the atmosphere, a large amount of heat is produced by the force of gravity. 4.The space shuttle is the only vehicle that can carry satellites back to the Earth from space so far. E 5.Hydrogen is used as rocket fuel because it burns easily and releases a large amount of energy. E 6.As the space shuttle moves round the Earth, its rocket engines are always on. E

3. ASSIGNMENT BOOK Unit 9 Part 1 9.5 B. Fill in the blanks This exercise is about the launching of a water rocket. Fill in the blanks with suitable words. 1. At launch, the pushing force is (a) ______________ (larger / smaller) than the (b) ______________ of the water rocket. The water rocket starts its motion and moves up with (c) ______________ (increasing / decreasing) speed. larger weight increasing

4. ASSIGNMENT BOOK Unit 9 Part 1 9.5 2. After a while, as some water has been pushed out of the rocket, the weight of the water rocket (d) ______________ (decreases / remains unchanged). However, the pushing force also (e) ______________ (decreases / increases). When the pushing force is less than the weight of the rocket, the rocket moves up with (f) ______________ (decreasing / steady / increasing) speed. decreases decreasing decreases

5. ASSIGNMENT BOOK Unit 9 Part 1 9.5 3. When all the water has been pushed out, the pushing force becomes (g) ______________ (zero / maximum). The rocket (h) ___________________________ ________________ (stops at once / continues to move up with decreasing speed). At its maximum height, the speed of the rocket becomes (i) ______________ (zero / maximum). zero continues to move up with decreasing speed zero

6. ASSIGNMENT BOOK Unit 9 Part 1 9.5 C. Questions Both will move towards each other. (a)Who will move when either Paul or Mary pulls the rope?(1 mark)

7. ASSIGNMENT BOOK Unit 9 Part 1 9.5 Both will move towards each other. Forces always occur in pairs. (b) Who will move when both Paul and Mary pull at the same time?(1 mark) (c) What property of forces does this experiment show?(1 mark)

8. ASSIGNMENT BOOK Unit 9 Part 1 9.5 2. The diagram below shows a balloon-powered rocket car. When the air inside the balloon escapes through the plastic straw, the car will move forward. balloon plastic straw

9. ASSIGNMENT BOOK Unit 9 Part 1 9.5 Add some lubricating oil to the wheels and axles. (or Add ball bearings to the wheels.) (b) Suggest ONE method to make the car roll more smoothly on the floor.(1 mark) As the balloon pushes the air out, the air also pushes back the balloon. The car moves forwards. (a) Explain why the car can move forward.(2 marks)

10. ASSIGNMENT BOOK Unit 9 Part 1 9.5 3. The photo below shows a rocket at the moment of lift-off. (a) Draw two arrows in the above photo to show the weight and the pushing force acting on the rocket. (2 marks) pushing force weight

11. ASSIGNMENT BOOK Unit 9 Part 1 9.5 The pushing force is greater than the weight. The pushing force is produced by ejecting hot gases downward from the rocket. The long and narrow design can help reduce air friction when the rocket is moving through the atmosphere. (b)Which of the two forces is greater?(1 mark) (c) How is the pushing force produced?(2 marks) (d) Why does the rocket have a long and narrow shape?(1 mark)

12. ASSIGNMENT BOOK Unit 9 Part 1 9.5 4. (a)The photo on the right shows the return capsule of Shenzhou 5. You can see that there are some burnt marks on it. This indicates that the capsule has been exposed to intense heat. The heat is produced when the surface of the capsule rubs against air at a very high speed. (i) How is the heat produced?

13. ASSIGNMENT BOOK Unit 9 Part 1 9.5 Cover the capsule with insulating materials. (b)The photo below was taken by Yang Liwei himself. You can see that his pen was floating inside the capsule. (ii) How can we protect the capsule from the intense heat?

14. ASSIGNMENT BOOK Unit 9 Part 1 9.5 Yes (ii) Is there any force of gravity acting on the pen? (1 mark) Weightlessness (i) Name this phenomenon. (1 mark)

15. ASSIGNMENT BOOK Unit 9 Part 1 9.5 5.(a)Label the following diagram with these words: rocket engines, external fuel tank, orbiter and solid rocket booster.(4 marks) external fuel tank solid rocket booster orbiter rocket engines

16. ASSIGNMENT BOOK Unit 9 Part 1 9.5 liquid oxygen and hydrogen They provide extra pushing force during lift off. Solid rocket boosters and orbiter. a satellite / Hubble Space Telescope (b) What are stored inside the external fuel tank? (2 marks) (d) Which parts of the space shuttle are reusable? (2 marks) (c) What is the function of the two solid rocket boosters?(1 mark) (e) State one object that the orbiter may carry into space during a normal mission. (1 mark)