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Professional English

Cambridge English for

Engineering

UNIT 10

case study

Roller coaster engineering

Part 1

a Discuss the following question about amusement park rides. What are the most exciting or terrifying amusement park rides you’ve been on? Describe them and what it was like to ride on them.

b A well-known type of amusement park ride is the roller coaster. Write a non-

technical definition, of 20 to 30 words, to describe a roller coaster in the space provided. Use some or all of the words in the box below to help you. bend   ​corkscrew   ​curve   ​ down   ​loop   ​slope   ​steep   ​track   ​train   ​up

Roller coaster:

Part 2 a The words in 1–10 below are physics terms which can be used to describe how

roller coasters work. Match them to the descriptions in a–j. 1 heat energy a energy in the form of movement 2 kinetic energy b energy stored in things that are hot 3 potential energy c stored energy that will allow an object to move (fall) due to gravity 4 G-force d speed in a certain direction 5 centrifugal force e increase speed 6 velocity f reduce speed 7 friction g pushes things outwards as they turn 8 inertia h pushing/pulling due to acceleration/deceleration 9 decelerate i resistance generated when two surfaces rub together 10 accelerate j resistance to acceleration or deceleration due to an object’s mass

b Complete the science magazine article on page 2 about how roller coasters work, using the physics terms from Exercise a (1–10).

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Cambridge English for Engineering Cambridge University Press 2011   www.cambridge.org/elt/englishforengineering

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UNIT 10 Roller coaster engineering

Roller coasters: how they work On a traditional roller coaster, the train begins by going slowly up a steep slope at the start of the track. Generally, the train is pulled up this slope by a moving chain located below the track, which is driven by an electric motor. When the train reaches the top of the slope, it has (1)  . This means it has the ability to descend due to the force of gravity. Therefore, the train can now produce (2) (that is, movement) without needing more power from the motor. The next section of track has a steep downward slope. This allows the , increasing its (4) as it goes train to (3) down the slope. This, together with the mass of the train and passengers, gives the train enough (5) to coast for a fairly long distance, without power. The rest of the track can include upward and downward slopes, curves, loops and corkscrews. These exert forces of . resistance, which progressively cause the train to (6) These forces are: g ravity, causing resistance as the train goes up slopes l (7) – the resistance of the wheels rubbing against the track and against their bearings and axles. This converts kinetic energy to (8) , increasing the temperature of the wheels. Roller coasters do not only have wheels running on top of the rails. They also have ‘upstop wheels’ below the rails and ‘guide wheels’ at the sides of the rails, to hold the train on the track. l

On sections of track with curves and loops, friction is greatly increased , which tries to push the train by (9) outwards as it turns. This presses the wheels hard against the track, generating high frictional resistance and, as a result, high temperatures. This force also pushes the passengers into their seats, generating the (10) that roller coasters are famous for.

Part 3

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Using the information in the article and your own technical knowledge, talk to a partner about the design of roller coaster wheels. Then give a short talk to sum up your thoughts. Discuss: 1 the different forces and conditions the wheels, axles and bearings of the train need to cope with 2 the implications of using larger or smaller wheels 3 the suitability of wheels made from different materials The following sections from Cambridge English for Engineering may be useful. ●●

Unit 2 – Describing specific materials (pages 14 and 15), Categorising materials (pages 16 and 17) and Specifying and describing properties (pages 18 and 19)

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Unit 5 – Describing types of technical problem (pages 38 and 39)

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Unit 9 – Discussing causes and effects (pages 76 and 77)

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Unit 10 – Discussing performance and suitability (pages 78 and 79), Describing physical forces (pages 80 and 81) and Describing capabilities and limitations (pages 84 and 85) Cambridge English for Engineering Cambridge University Press 2011   www.cambridge.org/elt/englishforengineering

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UNIT 10 Roller coaster engineering

Part 4 a Read the article extract, below, about ‘launched roller coasters’. Sum up how these are different to traditional roller coasters.

Many 21st century roller coasters differ from traditional rides in one way: they are ’launched‘. This means that, instead of being slowly pulled up the first slope by a chain, the roller coaster has a powerful launching system to accelerate the train rapidly along a flat section at the start of the track. This gives the train enough inertia to climb the first steep slope. Kingda Ka, the world’s fastest and tallest roller coaster at Six Flags Great Adventure in New Jersey, USA, has a launch system which accelerates the train from 0 to over 200 km/h in 3.5 seconds – an acceleration of about 1.5 G.

b Now imagine you are back in the 1990s, when the first launched roller coasters

were developed. You and your partner are research and development (R&D) engineers working for a roller coaster manufacturer. Come up with some ideas – in general terms – for suitable types of launch system. The systems should be:

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safe and reliable

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powerful enough to produce an ‘exciting’ amount of acceleration

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cost-effective to operate and maintain.

Prepare a short talk to explain your ideas.

Cambridge English for Engineering Cambridge University Press 2011   www.cambridge.org/elt/englishforengineering

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Professional English

Cambridge English for

Engineering

UNIT 10

TEACHER’S NOTES

Roller coaster engineering

Part 1

a Invite students to discuss the question in pairs, or as a group. b Ask students to complete the definition, either working in pairs or individually. The words in the box may also be useful for understanding the reading text in Part 2 and the discussion task in Part 3.

Compare students’ definitions with the Cambridge Advanced Learner’s Dictionary definition below. You could write it up on the board. Cambridge Advanced Learner’s Dictionary definition of ‘roller coaster’: an exciting entertainment in an amusement park, which is like a fast train that goes up and down very steep slopes and around very sudden bends

Extension activity: defining roller coaster

Ask students to discuss the meaning of the two verbs from which roller coaster stems: ‘to roll’ and ‘to coast’. Then compare them with the Cambridge Advanced Learner’s Dictionary definitions below. Cambridge Advanced Learner’s Dictionary definition of ‘roll’ and ‘coast’ (in this context): roll /rəʊl/ to (cause to) move somewhere by turning over and over or from side to side

coast /kəʊst/ to move forward in a vehicle without using the engine, usually down a hill

Part 2

Students complete both tasks in pairs. Answers a  2 a   ​3 c   ​4 h   ​5 g   ​6 d   ​7 i   ​8 j   ​9 f   ​10 e b 1 potential energy   ​2 kinetic energy   ​3 accelerate   ​ 4 velocity   ​ 5 inertia   ​ 6 decelerate   ​7 friction   ​8 heat energy   ​ 9 centrifugal force   ​ 10 G-force

Part 3

Ask students to read the article extract in Part 2 again. Focus on the meaning of the following terms in the text: axle /ˈæk.sƖ/ a shaft (bar) connected to the centre of a wheel or connecting a pair of wheels, and also connected to the chassis of a vehicle (a short axle for just one wheel is sometimes called a stub axle) bearing /ˈbeə.rɪŋ/ a part fixed around a shaft at the point where the shaft is connected to a machine or chassis, allowing the axle or shaft to spin with a minimum of frictional resistance and wear (bearings often contain metal balls, called ball bearings, which are designed to roll)

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Cambridge English for Engineering Cambridge University Press 2011   www.cambridge.org/elt/englishforengineering

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UNIT 10 Roller coaster engineering

You could show this photo of roller coaster wheels: http://en.wikipedia.org/wiki/File:Roller_coaster_wheels.jpg

Students then complete the task in pairs, then report back to the group with their thoughts. Suggested answers 1 The surfaces of the wheels that are in contact with the track, and also the points of contact between the wheels, bearings and axles, need to be able to resist friction. The wheels also need to cope with the heat generated by friction. The wheels, bearings and axles have to cope with the forces of expansion and contraction as they continually heat up, due to friction, and then cool down as the roller coaster repeats the ride cycle. The wheels must resist the centrifugal force of the wheel itself spinning. This will generate tension (stretching force) as the centrifugal force tries to push the material of the wheel outwards (like the pastry of a pizza stretching outwards as the cook spins it round). The wheels and bearings must also resist compression (crushing force) when they are forced against the rails by the centrifugal force acting on the train as it turns through curves and loops. The axles need to cope with shear force (scissoring force) as the train is forced against the track as it turns through curves and loops. 2 The main advantage of smaller wheels is that they are more compact, making them easier to fit below the train. Smaller wheels also reduce the total mass of the train – although this isn’t necessarily an advantage, as a roller coaster train needs mass to give it inertia to keep it rolling. Another advantage of smaller wheels is that their thickness is greater relative to their diameter – i.e. they are less slender than larger wheels of the same thickness. ‘Taller’, more slender wheels would buckle more easily when compressed against the rails. The disadvantage of smaller-diameter wheels is that, for a given velocity, they spin faster than larger wheels. This creates more frictional resistance (greater speed = greater friction) and, as a result, generates higher temperatures. The centrifugal force caused by the wheel itself spinning is also higher with smaller wheels, due to the higher rotational velocity. 3 Strong metal, such as steel, is a good material for resisting the different forces acting on the wheels. However, metal-only wheels running on the metal track would be problematic, as they would be noisy, transmit a lot of vibration to the train and passengers, and would also cause the track (which is expensive to replace) to wear quite quickly. Solid tyres made from polymers (plastics), such as polyurethane, are better, as they give a quieter, softer ride, don’t wear the track and can be replaced fairly cheaply. The disadvantage of polyurethane on extreme roller coasters is that it can get too hot and melt. Instead, especially tough rubber can be used, similar to that used in aircraft tyres (which need to cope with high levels of friction on landing).

Part 4 a Students read the article extract and complete the task. You could follow up by showing a ‘front seat’ video of the Kingda Ka roller coaster: http://www.youtube.com/watch?v=xTNcnJS-a2M&feature=fvsr

b Students complete the role play discussion task in pairs, followed by

presentations to the group. You can use the following Wikipedia link to look at the launch systems actually used on roller coasters: http://en.wikipedia.org/wiki/Launched_roller_coaster

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Cambridge English for Engineering Cambridge University Press 2011   www.cambridge.org/elt/englishforengineering

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Cambridge English for Engineering - Worksheet - Roller Coaster Engineering