.......and some fun!

Brian CattBrian Catt

AirIs a gas, light but..............Has weight – 1 thousandth of waterI cubic metre weighs 1 kilogram10 tons per square metre above you (8 cars)Resists objects passing through it by friction –

example?

Is compressible – squashableCan store energy – that will propel our rockets

Now for an experiment….

WaterIs a liquid – a different structure inside

Can also be a gas or a solidHeavier – I kg per litre, 1,000 times airNOT compressibleCannot store energyBut essential to propelling the rocket

Why?

Action and ReactionEvery action has an equal opposite reactionSomething goes one way, something else must

go the other way Lift Off

How they move depends on their weightshttp://www.youtube.com/watch?v=RZjhxuhTmGk&feature=related

AND NOW - another demo!

• We need to have the best mix of water and air

• Air to provide the energy• Water to provide mass

Our Rocket Experiment

GravityWhat goes up must come down, well mostlyGravity gives things weightGravity is a property of mass, bigger = more

gravityThe earth is very bigThe moon is a tenth the mass of the EarthBut gravity is still a weak forceCan be resisted relatively easily by stronger forcesWhat slows the fall?The air – when its there…… http://www.youtube.com/watch?v=MQ7N6V-YKJ8

STEP OUTSIDE......

Changing big things –What Happens?

No WaterWater, no fins AND no weightWater + Weight with no FinsWater + Fins but no weightFins + Weight + Water

What Did We Learn?We create an actionTo which there is an equal and opposite reactionAir is compressible, so can store the energy to launchBut air is light so reaction of bottle is smallWater is incompressible - but much heavier than air80g Bottle is much lighter than heavy waterSo bottle goes away much faster than does the water in

the opposite directionThe bottle is slowed by the friction of the airGravity pulls it back to the ground

The Sun is Bigger