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Space journey —launching
9.4
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The force of gravity keeps us on the Earth’s surface.
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How can we overcome the force of gravity and travel into space?
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The principle behind a rocket launch
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Forces always occur in pairs
Action and reaction Forces always occur in pairs Action (作用力) Reaction (反作用力)
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9.7 Experiment video Pull and push 1 A B rope wooden trolley
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9.7 a What happens? Both move towards each other. Pull Hold
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9.7 b A B force acting on B by A force acting on A by B
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9.7 c What happens? Both move towards each other. Pull Pull
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9.7 2 A B wooden trolleys
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9.7 a What happens? Both move away from each other. Push gently
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9.7 b A B force acting on A by B force acting on B by A
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9.7 What happens? c Both move away from each other. Push gently
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9.8 Forces between a pair of trolleys 1 trigger trolley A B
Experiment video Forces between a pair of trolleys 1 trigger trolley A B
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9.8 2 What happens to the trolleys? A B
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9.8 What happens to the trolleys? Trolley A moves _______________.
Trolley B moves _______________. 2 to the left to the right A B
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9.8 3 force acting on A by B force acting on B by A
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Action and reaction action-and-reaction pair A B
pulling force acting on A by B pulling force acting on B by A A B
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Action and reaction action-and-reaction pair A B
pushing force acting on A by B pushing force acting on B by A A B
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Are the sizes of action and reaction the same or different?
B
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9.9 Comparing the sizes of action and reaction 1 A B newton balance A
Experiment video Comparing the sizes of action and reaction 1 newton balance A newton balance B A B
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9.9 2a record record pull hold A B
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9.9 3 A B force acting on balance B by balance A
force acting on balance A by balance B A B
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9.9 4 Compare the readings of balances A and B. What can you tell from the results? The readings are the same. The action and the reaction are of the same size.
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Action and reaction When we exert a force on an object,
a force of equal size in the opposite direction will act on us. A B force acting on balance A by balance B
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act on different bodies
Action and reaction act on different bodies A B
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the swimmer is pushed to the other side of the pool
Action and reaction force exerted on the pool side by the swimmer force exerted on the swimmer by the pool side the swimmer is pushed to the other side of the pool
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the diver is allowed to jump off the diving board
Action and reaction the diver is allowed to jump off the diving board force exerted on the diver by the diving board force exerted on the diving board by the diver
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Action and reaction Forces always occur in pairs.
When object A exerts a force on object B, object B exerts a force of equal size on object A in the opposite direction. These two forces are an action-and-reaction pair.
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How does the rocket produce the force to push itself upwards?
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9.10 Launching a water rocket 1 air pump water rocket water trigger
Experiment video Launching a water rocket 1 air pump water rocket water trigger
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9.10 What happens? The water inside the water rocket moves ____________. The water rocket moves ____________. 3 downwards upwards
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9.10 4 force acting on rocket by water force acting on water by rocket
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How does a rocket propel itself?
Makes use of action and reaction 3D animation
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How does a rocket propel itself?
pushes the rocket upwards reaction the rocket ejects hot gases downwards
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How does a rocket propel itself?
When a rocket is launched, it ejects hot gases downwards and the reaction pushes the rocket upwards.
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Rocket design Problems when launching a rocket:
air resistance When the rocket is flying at a high speed, air resistance is very large.
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Rocket design Problems when launching a rocket:
There is no air in space, the rocket fuel cannot burn. fuel oxygen high temperature
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Rocket design Problems when launching a rocket:
The force of gravity acting on the rocket is very large. force of gravity
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Rocket design Problems when launching a rocket: large air resistance
no air for burning fuel in space large force of gravity How can these problems be solved?
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Rocket design Problems when launching a rocket: large air resistance
no air for burning fuel in space large force of gravity
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Streamlined shape designed to have a streamlined shape
air resistance is reduced
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Rocket design Problems when launching a rocket: large air resistance
no air for burning fuel in space large force of gravity
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Carrying its own supply of oxygen
no oxygen in space needs to carry its own supply of oxygen
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Carrying its own supply of oxygen
no oxygen in space oxidizer (used with solid fuels) need to carry its own supply of oxygen liquid oxygen (used with liquid fuels)
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Carrying its own supply of oxygen
Solid-fuel rocket Liquid-fuel rocket liquid fuel solid fuel grain liquid oxygen igniter combustion chamber nozzle nozzle
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Carrying its own supply of oxygen
Solid-fuel rocket Liquid-fuel rocket Structure more complicated simple
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Carrying its own supply of oxygen
Solid-fuel rocket Liquid-fuel rocket Structure fuel and oxidizer are mixed to form grains fuel and liquid oxygen are stored separately
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Carrying its own supply of oxygen
Solid-fuel rocket Liquid-fuel rocket Structure grains can be stored at room temperature fuel and oxygen are kept at low temperature and high pressure
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Carrying its own supply of oxygen
Solid-fuel rocket Liquid-fuel rocket Operation grains are burnt at launch fuel and oxygen are mixed and burnt at launch
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both produce a large volume of hot gases at launch
Carrying its own supply of oxygen Solid-fuel rocket Liquid-fuel rocket Operation both produce a large volume of hot gases at launch
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Carrying its own supply of oxygen
Solid-fuel rocket Liquid-fuel rocket Features solid fuels do not leak liquid fuel may leak and explode strong tanks to withstand the high pressure
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Carrying its own supply of oxygen
Solid-fuel rocket Liquid-fuel rocket Features smaller upward force is produced per unit mass of fuel greater upward force is produced per unit mass of fuel
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Carrying its own supply of oxygen
Solid-fuel rocket Liquid-fuel rocket Features the burning process and pushing force cannot be adjusted the burning process and pushing force can be adjusted
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in gas state at room temperature and pressure
Carrying its own supply of oxygen Liquid-fuel rocket Common example of liquid fuel: liquid hydrogen in gas state at room temperature and pressure
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(takes up less space; more can be stored in the fuel tank)
Carrying its own supply of oxygen Liquid-fuel rocket hydrogen gas cooled and compressed liquid hydrogen (takes up less space; more can be stored in the fuel tank)
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9.12 Experiment video Burning hydrogen 1 hydrogen
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9.12 What happens? It burns with a ‘pop’ sound. 2 burning splint
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Carrying its own supply of oxygen
pop mini-explosion
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+ + Carrying its own supply of oxygen pop hydrogen oxygen
large amount of heat energy and light energy + water (in gas state)
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Carrying its own supply of oxygen
liquid hydrogen liquid oxygen mixed and burnt
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Carrying its own supply of oxygen
No pollutant! large pushing force large amount of hot gases rushes out
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Carrying its own supply of oxygen
But if not handled properly leakage may cause explosion
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Rocket design Rockets have a streamlined shape to reduce air resistance when they travel into space.
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Rocket design Rockets carry their own supply of oxygen for burning fuels.
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Rocket design There are two main forms of fuels used in rockets: __________ and __________. solid fuels liquid fuels
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Rocket design Liquid hydrogen is a common fuel used in rockets. Leakage of hydrogen into the air may lead to an ___________. explosion
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Rocket design Problems when launching a rocket: large air resistance
no air for burning fuel in space large force of gravity
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rocket divided into two to four stages
Multi-stage design great mass 3D animation great force of gravity rocket divided into two to four stages
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Multi-stage design Long March 2F rocket two stages
each stage has rocket engine and fuel supply
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spacecraft second stage booster rocket first stage rocket engine
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Multi-stage design When the fuel in the first stage is used up …
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Multi-stage design the fuel in the second stage starts to burn to push the rocket further up the stage drops off to reduce the mass
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Multi-stage design When the fuel in the second stage is used up, it also drops off.
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Multi-stage design overall weight decreases as the stages drop off one by one easier to overcome the force of gravity and fly into space
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Multi-stage design A rocket has different _________ which will drop off to reduce its mass as it travels towards space. stages
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Some modern rockets and their designs
Saturn 5 rocket 3D model First launched in 1967 Carried the first man to the Moon Height: 111 m USA
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escape tower Apollo spacecraft 3rd stage rocket 2nd stage rocket
Saturn 5 rocket Apollo spacecraft 3rd stage rocket 2nd stage rocket 1st stage rocket
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liquid hydrogen tanks liquid oxygen tanks liquid fuel tank
Saturn 5 rocket liquid hydrogen tanks liquid oxygen tanks liquid fuel tank rocket engine
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Carried the first Chinese into space
Long March 2F rocket First launched in 1999 Carried the first Chinese into space Height: 59 m China
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escape tower Shenzhou spacecraft 2nd stage rocket 1st stage rocket
Long March 2F rocket Shenzhou spacecraft 2nd stage rocket 1st stage rocket
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Long March 2F rocket rocket fairing oxidizer tanks liquid fuel tanks
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Long March 2F rocket booster rocket rocket engines
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The first reusable spacecraft
Space shuttle First launched in 1981 The first reusable spacecraft Height: 56 m USA
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liquid oxygen tank external tank orbiter liquid hydrogen tank
Space shuttle liquid oxygen tank external tank orbiter liquid hydrogen tank solid rocket booster rocket engines
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Carried artificial satellites into orbit
Ariane 5 rocket First launched in 1996 Carried artificial satellites into orbit Height: 46–52 m Europe
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Ariane 5 rocket 2nd stage rocket 1st stage rocket
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liquid hydrogen tanks liquid oxygen tanks solid rocket booster
Ariane 5 rocket liquid hydrogen tanks liquid oxygen tanks solid rocket booster
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Ariane 5 rocket rocket engines
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Saturn 5 rocket Developed by German scientist, Wernher von Braun (1912–1977)
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9.3 Rocket scientist – Wernher von Braun
Germany 1924 Wow! My toy truck with firecrackers flies up like a rocket. 12-year-old Wernher von Braun
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9.3 What’s out there in space?
A rocket my be able to send us into space!
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9.3 To understand how rockets work, I must study Physics and Mathematics well. 1930
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9.3 After graduation from the University of Berlin, Braun began to develop rockets as weapons for the army. 1934
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9.3 My team successfully developed the V-2 rocket as missiles. 1942
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9.3 Germany attacked Britain with V-2 rockets in World War II.
1944 The rocket works well but it is used for the wrong purpose.
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9.3 Braun moved to the USA in 1945.
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9.3 There, he developed the Saturn 5 rocket, which sent the first humans to the Moon. USA 1969
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9.3 My dream has come true! I believe the Saturn 5 rocket will someday send humans to Mars. USA 1969
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9.3 1 How many years of hard work did Braun undertake to send the first humans to the Moon, since his graduation in 1934? 35 years (= 1969 – 1934)
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9.3 2 The rocket can be used as a weapon or as a tool for exploring space.
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9.3 2 Discuss with your classmates whether the invention of modern rockets does more harm or more good for humans.
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4 Draw arrows to show the corresponding reaction forces.
The reaction force is the force acting on ___________ by __________. 1 the hand the cup force acting on the cup by the hand
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4 2 The reaction force is the force acting on ___________ by __________. the Earth ball the ball Good! Earth force of gravity acting on the ball by the Earth
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