1. Cruising the waves on our maritime motorways
The need for speed:
Cruising the waves on our maritime motorways

2. Session outline Why shipping is important How ships move
The forces acting on ships – A look
at drag
Calculating speed and distance-
time graphs

3. 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
Shipping is of importance to us all
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In the UK in particular, shipping employs 250,000 people in the UK,
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and is the second biggest earning industry after agriculture generating a massive £37 billion to the UK economy per year, that’s £162 per second (shown in the did you know box).
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As well as economic benefits, the shipping industry also provides social benefits as well, including a source of protein in our diets
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and the delivery of over 95% of the products we use on a day-to-day basis right to our doorsteps!
The ability of ships to perform their tasks depends a lot on the design of the ships themselves.
Ships need to be efficient to carry out their jobs. Part of this efficiency looks at their speed.
British shipping earns the UK economy £162 per second!*
*SeaVision UK
Did you know?

4. How ships are designed Considering the shape of ships
When naval architects and marine engineers design
and build ships, they have to follow a certain number
of rules…
Two of the most important are:
1 They have to float and stay upright – Looks at Buoyancy and Stability of ships
2 They have to be able to move – Looks at Power (thrust) and Drag on ships
Read through text
Click one – read through text
Click two – read through text
Lets address each in turn…
In particular we are going to focus on the fact that ships must be able to move.

5. 2 - Power (thrust ) and Drag
When forces are balanced: ships are stationary
Thrust Force = Drag Force
However,
Ship’s engines must provide enough power (thrust) to overcome drag (water resistance, which is a form of friction) so that:
Thrust Force > Drag Force
So that ship’s can move
through the water and
transport cargo from A to B!
Click one
When forces are balanced ships are stationary
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i.e. the thrust force (provided by the engines of the ship through the combustion of fossil fuels) is equal to the drag force on the ship (provided by water resistance)
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However, ship’s engines need to provide enough power (thrust) to overcome drag so that the thrust force is greater than the drag force
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And ships can move from A to B!
To go faster, the force of the engine needs to exceed that of water resistance.
Therefore, forces need to be unbalanced to increase speed.

6. Thermal energy Chemical energy Fuel How thrust is generated on Engine
Wasted energy
Chemical energy
Fuel
Engine
How thrust is
generated on
ships
Combustion
HC’s + O2  CO2 + H20
Propeller shaft
Oxygen
Work done
Friction
Kinetic energy
Wasted energy
For a bit of background, thrust is generated in ships through the combustion of fuel (often diesel oil) with oxygen in the engine. This provides work done which drives a propeller to generate forward motion. The process also generates waste heat energy and emissions.
Click one
For marine engines we generally start off with a fossil fuel, which in this case is oil. A ‘fuel’ is any substance which contains stored chemical energy that can be burned to release heat energy. How do you fossil fuels are created? (ask pupils)
(encourage pupils to say that the suns energy was absorbed by marine plants millions of years ago via the process of photosynthesis. As these plants, and the animals that ate them, died they fell to the seabed and got buried in mud and sand, forming fossils. More layers of mud and sand squashed the fossils, heating them under pressure which formed the crude oil we use today).
What form of energy do you think oil stores? (encourage pupils to say chemical) – Click two
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Oxygen is added to the fuel to start a chemical reaction inside the ships engine. (Ask pupils to name this chemical reaction. Encourage them to say combustion)
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It is important to understand that burning fuel does not make energy, it changes the energy stored inside the fuel from one form to another.
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To make ships move, chemical energy stored in the fuel is released as heat energy by combustion. This heat energy is used to heat steam which drives turbines and subsequently rotates a propeller shaft. (Ask pupils what form of energy they think the heat energy has been transferred to by turning the propeller shaft. Encourage pupils to say kinetic or mechanical energy).
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The propeller shaft is attached to a propeller, which spins with the rotation of the propeller shaft providing work in the form of thrust which drives ships forward!
There is just one problem, this process of energy conversion is by no means 100% efficient, and energy is converted to other, non-useful forms, at each stage.
(ask pupils to think of stages in the generation of thrust where energy might be converted to more non-useful forms. Encourage pupils to think about heat energy wasted from the engine, friction being generated during rotation of the propeller shaft, and sound energy being generated by rotation of the propeller).
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During combustion, some of the chemical energy stored in the fuel is lost as heat energy via exhaust gases, flue gases from the boiler and radiation from the boiler and engine for example, but is subsequently recovered in other processes as we shall learn more about later on.
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Some of the kinetic energy during rotation of the propeller shaft is lost as friction
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And some of the kinetic energy is also lost through sound energy from both the propeller and rotation of the propeller shaft
Let’s take a look at how auxiliary (electrical power) power is generated
Sound
Wasted energy
Thrust

7. The forces acting on ships: what a drag!
Drag slows ships
down
Unbalanced forces
makes things
happen
As ships move faster,
drag also increases!
Everything has a top speed. For ships, this depends on:
The force the engine can produce
The design of the ship
Drag
(water resistance)
Gravity
Thrust
(from engine)
Drag slows ships down.
Drag is caused when water particles hit the moving object and bounce off it. Each particle produces a tiny force that slows the object down.
Unbalanced forces
To move, the force of the engine needs to be bigger than the force of water resistance
For every force there is almost always a force acting in the opposite direction
Analogy for ships faster also resistance more. Swimming and walking through water.
Upthrust

8. The fastest ship in the world!
Water speed record:
m.p.h / km/h
"Spirit of Australia"
The greater the speed, the more particles hit the moving object per second and the greater the drag force becomes.
The fastest ship in the world, the Spirit of Australia is very well designed to reduce the effect of drag. Ask pupils to think of their ideas

9. Did you know?
The US Navy are using the natural streamlined design of open-water fish for inspiration in creating more speedy and efficient submarines
Here we have an example of the tuna fish, designed for speed with its streamlined shape. The US navy are even using the natural streamlined design of open-water fish for inspiration in creating more speedy for efficient submarines.

10. The Shape of Ships: Drag is bad
How resistant to drag a ship is has a lot to do with its shape:
Streamlining
Surface texture
Vs.
Curved
Straight edged
The drag on a ship has a lot to do with its shape.
Want to get the best shape for avoiding water resistance.
Streamlining can help to reduce drag because most of the particles get swept around it
Click one and two
Which of these shapes do you think would provide the most streamlined design for ships? Ask pupils why
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Which of these surface textures do you think would provide the most streamlined design for ships? Ask pupils why
For more information about how marine engineers keep ships’ hulls smooth during sailing, please see Paint Science in Module C) Shipping and the Environment available from the Inspiring Seas website
Vs.
Smooth
Rough

11. Physics in the real world: Exactly how its done in the business!
When ships are commissioned and designed by Naval Architects, a hugely scaled down version is made from wood, wax or fibre glass and is tested for efficiency in a piece of equipment known in the business as a ‘towing tank’.
The tank has a run line for the model ship to be attached to, which then draws the ship through the water. The resistance on the ship model can be measured and with some careful maths marine engineers can work out whether the ship, when built to full size and out of steel, would be seaworthy. That’s some pretty important physics!
Newcastle University’s Towing Tank

12. ‘Fouling’ – What is it?
Some organisms start out in life as tiny larvae
As they grow, some need to find a hard surface to settle on
Larval barnacle
Larval
settlement
Adult barnacle
Sometimes this hard surface can be the hulls of ships!
The organisms that do choose to settle here are referred to as ‘fouling’ organisms
One thing that can really slow ships down is the problem of fouling.
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When some marine organisms reproduce, the fertilised embryo develops into a larvae which floats around in the water column as part of the plankton.
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Although some of these larvae spend their whole lives in the water column, such as copepods, many need to find a place to settle out to grow to adult phase. One example is the adult barnacle.
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Space is often a limiting factor effecting population size in the marine environment, so sometimes the hard substrate these organisms settle on are the hulls of ships (as shown by the picture).
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These organisms are referred to as fouling organisms
A problem because it increases drag on ships

13. Why is it important for ships to be designed well?
…because it makes them more:
Cost effective: A streamlined shape lowers drag and the
amount of fuel needed to provide the power (thrust) to
move ships from A to B.
Environmentally friendly: lowering the amount of fuel
needed to transport ships from A to B means less
pollution to the atmosphere and surrounding
water.
Ask pupils what their ideas are:
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First of all an efficient design makes shipping a more cost effective industry. If ships have a streamlined design for example less water resistance is imposed on the ships hull. This reduces the power (thrust) required to overcome resistance and so less fuel is required to move ships from A to B. This means for cargo shipping for example the end products (bought by us the consumers) are actually cheaper to buy because it cost less to get them to us!
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Not only this but by reducing the amount of fuel required to power ships we also make shipping a more environmentally friendly industry as less pollution is generated in the form of oil pollution and emissions.
Ask pupils what the effects of fossil fuel emissions are (looking for acids in the environment and global climate change). More information on shipping and the environment can be found in Module C) from the Inspiring Seas site.

14. What is speed? How do we measure it?
How far something travels in a given amount of time
How do we measure it?
SIDOT
Speed Is Distance Over Time: D T S
Measured in:
Metres per second – m/s, or ms-1
Miler per hour – m.p.h
Kilometres per hour – km/h, or kmh-1
Golden Rule: ALWAYS a distance unit
per time unit!

15. We can show speed as a graph
400
300
Distance (km)
200 D T S
100
Called a distance-time graph.
Ask pupils:
How far had the ship gone after 2 hours?
How far had the ship gone after 6 hours?
When are the forces acting on the ship balanced?
When was the ship travelling the fastest? 2 4 6 8 10
Time (h)
Golden Rule: ALWAYS a distance unit
per time unit!

16. Plenary: Complete the need for speed calculations sheet.
Make up your own distance/time graph to show a
journey a cargo ship could make from one country to
the other.
Write about what is happening at each stage of the
journey and decide on a commodity your ship could be
carrying and label the countries your ship is travelling
from and to.