Sink or swim The buoyancy and stability of

Sink or swim? The buoyancy and stability of ships

Session outline Archimedes in practice – The science behind buoyancy (floating) Why ships need to float! – the value of shipping How do ships need to float? – A bit about moments and stability of ships

Archimedes Principle “An object in a fluid experiences an upward force equal to the weight of the fluid displaced by the object”

Archimedes in practice: Explains why steel ships float! Ball: displaced water weighs less than the ball - SINKS Hull: displaced water weight is the same as the hull weight – FLOATS Hull Ball

Archimedes in practice: Explains why steel ships float! Forces are balanced Upthrust of water Upthrust Weight of ship Weight

How do we work out if something floats? The maths behind theory: Which variables do we need to look at? volume? den sity ? t? h ig e w ma ss?

We look at its DENSITY! The maths behind theory: Density = Mass Calculating mass: In g Volume M Calculating volume: (cm 3) D Length x Height x Width V h w l Golden Rule: If something has a density of <1 g/cm 3 it will float in water!

The Benefits: Shipping in our everyday lives Employs 250, 000 in the UK Generates £ 37 billion to UK economy per year The fishing industry provides us with a good source of protein for our diets Cargo shipping provides us with 95% of the products we use on a day-to-day basis Did you know? British shipping earns the UK economy £ 162 per second!* *Sea. Vision UK

But we need ships not just to float… …but to float upright (stability) Is this ship floating? ? ?

Just a moment… Moment Applied Centres of gravity and buoyancy New centre of buoyancy when ship is upright ship rolls

All or nothing! OR The ship rights itself, ‘bouncing back’ from the moment applied The ship capsizes!

What influences an object to right or capsize? Centre of BUOYANCY Needs to be central and low Centre of GRAVITY Needs to be central and medium height

Practical time! Sink or swim? The Scenario Captain Eco. can’t work out what to base his new super ship design on! He has provided you with a range of materials and objects to test for stability and buoyancy See if you can give Captain Eco a hand to recommend which material/object would be the best choice for a perfectly stable and buoyant ship! Good luck. Captain Eco. is counting on you